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Articles and tips on digital tools, productivity, and PDF technology
Finding the Accurate Qibla Direction: Why a Straight Line on a Map Isn't Enough
Finding the qibla direction sounds simple — a straight line toward Mecca on a map — but that line is wrong for most of the world. This guide explains why, and how a qibla tool actually calculates the correct bearing using great-circle geometry.
Margin vs Markup: Why Confusing Them Prices a Sale Below What You Meant
You want a certain profit rate, so you add it straight onto the cost, assuming that is your profit from the selling price. The problem is these are two different numbers for the same sale, and confusing them means pricing below what you intended without noticing. This guide explains the difference with a real example and when to use each calculation.
Due Date Calculator From Your Last Period: How the Date Is Worked Out
The estimated due date is a projection, not a fixed appointment — worked out from your last period, a conception date, or an IVF transfer, and it shifts with your cycle length. This guide explains how each starting point is calculated, and why the number can differ between calculators.
Accurate Prayer Times: Why Fajr and Isha Differ Between Apps
Open two prayer-time apps on the same day and Fajr or Isha can differ by ten minutes or more. This guide explains why that gap is real, and how to pick the calculation method and madhab that match what your own community follows.
Convert PowerPoint to PDF Without Fonts or Layout Breaking
A presentation that looks perfect on your laptop can open completely differently on the meeting room projector or a client's machine — a font swapped, text spilling off a slide, a graphic shifted out of place. This guide explains why, and how converting to PDF fixes it before any important meeting.
Passport Photo Size: How to Prepare an Official ID Photo Yourself
A photo cropped to the wrong size is a common reason an official application gets rejected or delayed. This guide covers the different official sizes for passports, visas and local documents, and how to prepare a compliant photo yourself, no studio visit needed.
Percentage Calculator: How to Work Out Discounts, Increases and Percent Change Without Mistakes
Three percentage questions come up every day: what is X% of Y, what percent is X of Y, and how much did a value change. This guide explains each with its formula and examples, and points out the classic traps such as a discount followed by an increase.
How to add a text watermark to a PDF without ruining readability
You send a quote or a draft contract and later find it circulating, or credited to someone else. A clear text watermark on every page fixes that, but the wrong opacity or size makes the document hard to read. This guide explains how to balance protection with readability.
How to remove the recurring password from a monthly PDF statement
A bank statement or bill arrives as a PDF every month with the same password, and you type it in again just to open the file or forward it to your accountant. This guide covers permanently removing the password from a file you already know the password to and have the right to open.
Convert PDF to an Editable Word Document Without Losing Layout
A contract or report arrives as a PDF and you don't have the original Word file, yet you need to edit just one paragraph. This guide explains how PDF to Word conversion pulls out text and layout automatically, where alignment issues show up, and how to fix them instead of retyping the whole document.
Convert PDF to Editable PowerPoint Slides Without the Source File
You only have a presentation as a PDF, and you need to edit one slide for a new pitch. This guide explains how PDF to PowerPoint conversion turns each page into an editable slide, where elements need manual repositioning afterward, and when starting from a fresh template is actually faster.
Convert PDF to PDF/A: why some government systems reject a normal PDF
You try to upload a normal PDF to a government portal or archive system and it gets rejected because PDF/A specifically is required. This guide explains the difference between a regular PDF and PDF/A, and why some files fail even though they open fine on your own device.
How to convert PDF pages to JPG images without losing quality
A design platform only accepts images, not PDFs, and you have a three-page PDF design that needs uploading as separate images. Converting a PDF to JPG sounds simple, but picking the wrong resolution either blurs the text or produces needlessly heavy images. This guide explains how to pick the right resolution and quality for each use.
Extract Tables from PDF to Excel Without Retyping Every Number
A financial report arrives as a PDF with a table of hundreds of numbers you actually need in Excel to analyze or chart. This guide explains how PDF to Excel conversion pulls the table out automatically, where merged cells need a manual check, and why manual retyping is riskier than any conversion mistake.
How to split a PDF into separate files by page or range
A fifty-page PDF when you only need ten pages of it. Splitting a PDF solves this in three different ways depending on what you actually need: every page on its own, a specific range, or an even split every N pages. This guide explains when to use each one and where people usually get the range wrong.
How to sign a PDF electronically without printing it first
A contract arrives as a PDF and you need to sign it, so you think about printing, signing by hand, and scanning it back in. This guide explains how to place your signature directly on the digital file with no printer or scanner, where to put it, and when this is enough versus when you need something stronger.
How to permanently rotate a PDF page without rescanning it
You open a PDF and find one or two pages flipped sideways, and your PDF viewer only rotates them for viewing, so they snap back to wrong the moment you close the file or send it to someone else. Permanently rotating a PDF fixes this for good, and this guide explains the difference between temporary and permanent rotation and when you need each.
How to fix a corrupted PDF that won't open, step by step
You open a PDF and get a vague error, a blank page, or a program that just hangs. This guide explains the common causes of PDF corruption, how a repair tool tries to recover the file, and when a file is actually recoverable versus when it isn't.
How to password protect a PDF before you email it
Emailing a contract or financial report with no protection means anyone who intercepts the message, or it gets forwarded by mistake, can open it and read everything. This guide covers adding a real password to a PDF, and sharing that password without undoing the protection.
How to add page numbers to a PDF automatically, the right way
You print a hundred-page report with no numbers, the pages fall out of order, and you lose any way to put them back together. This guide explains how to add automatic page numbers to a PDF, where to place them, and how to handle a cover page you don't want numbered at all.
How to delete or reorder pages in a PDF without rebuilding the file
A presentation exported as a PDF picks up a blank page in the middle, or a report needs its appendix moved to the end instead of where it currently sits. Organizing PDF pages fixes both problems without rebuilding the file from scratch. This guide explains the difference between deleting and reordering, and when you need each.
How to Convert a Scanned PDF into Searchable, Copyable Text
A scanned PDF looks like a normal file, but its text is really just a picture — nothing to select, copy, or search. This guide explains how OCR turns that picture into real text, where mistakes creep in, and when the result still needs a manual check.
How to merge PDF files into one document, without losing quality
Merging PDFs sounds trivial until the page order scrambles or the file size doubles for no reason. This guide explains how merging actually works, where people go wrong, and when to compress before or after combining files.
How to check a PDF's page count and file info before you open it
Before uploading a PDF to a system that caps submissions at twenty pages, or sending one to someone who asks about its creation date and author, you need those details without opening the file page by page or guessing. A PDF info tool shows all of it in seconds — this guide explains how to read and use the result.
Markdown Previewer: Write in a Simple Syntax, See the Result Instantly, and Copy Clean, Safe HTML
Markdown is a simple writing syntax understood by GitHub and hundreds of platforms. This guide explains its key rules from headings to tables, why Sahel's previewer does not pass raw HTML or dangerous links through, and how to copy clean output for your site.
Lorem Ipsum Generator: Why Designers Use Placeholder Text and How to Use It Properly
Text that fills the page before anyone has written the real content. This guide explains where Lorem Ipsum comes from, why it beats repeating real words, when it does harm, and how to generate Latin or Arabic filler in the amount you need.
Sort Lines, Remove Duplicates and Clean Text Lists: Quick Tools for Long Text
A mailing list full of duplicates, scattered file names, words that need alphabetical order. This guide explains how to process text line by line: alphabetical and natural sorting, removing duplicates, reversing, numbering and cleaning, and where the usual mistakes happen.
How to Decode a JWT and Read Its Claims: What Is Inside, and What the Signature Does Not Tell You
A JWT looks like a random string but it is three readable parts. This guide covers how to decode one, what each field inside means, why decoding it does not make it trustworthy, and why you should never type your secret key into a web page.
How to Format and Validate JSON: Finding the Exact Error Instead of Guessing
A JSON response squeezed into one line thousands of characters long, and an error message that never says where the problem is. This guide covers what a formatter actually does, why pinning the error to a line and column matters, and why some tools silently corrupt long IDs.
How to Check a File Checksum (SHA-256, MD5): Confirming a Download Is Untouched
A download page shows a long string called a checksum and never explains what to do with it. This guide shows how to compute the hash of any file or text, how to compare it with the published one, and why MD5 and SHA-1 are no longer fit for passwords.
GPA Calculator: How Grade Point Average Is Worked Out and What You Need to Reach Your Target
GPA is not a plain average of grades but an average weighted by credit hours. This guide explains the formula on 4.0 and 5.0 scales, how to fold a new term into your cumulative GPA, and how to find the grades you need to reach a target.
Unix Timestamp to Date: How to Tell Seconds from Milliseconds Before You Convert
A ten-digit number in your database means some date, but which one? This guide explains what a timestamp is, how to tell seconds from milliseconds and microseconds, and why guessing the unit wrong puts you off by a factor of a thousand.
How to Compare Two Texts and Find the Differences Line by Line
Two versions of a contract, a config file or a message, and you sense something changed but cannot tell where. This guide explains how text comparison works, when to ignore whitespace and letter case, and how to read the result without missing a line that matters.
CSV to JSON and JSON to CSV: Handling Commas, Quotes and Leading Zeros Correctly
A spreadsheet that must become data for an app, or an API response that needs to be a table. This guide explains the CSV rules most conversions get wrong: commas inside fields, quotes, multi-line values and numbers with leading zeros.
Cron Expression Explainer: What the Stars and Numbers Mean and When Your Schedule Will Really Run
Five fields decide when a scheduled job runs, and a mistake in one makes it run every minute instead of every hour. This guide explains each field, the star, comma, dash and step symbols, and the double-day rule that surprises everyone.
HEX, RGB and HSL Color Conversion, and Checking Contrast: Is Your Text Actually Readable?
A colour in the design file in one format and in the code in another, and grey text that looks readable to you but not to someone else. This guide explains the three formats, what a contrast ratio means, and when a pair of colours passes WCAG.
Base64 Encoding and Decoding: What It Is, and Why Most Tools Mangle Non-Latin Text
Base64 is not encryption, not protection, and not compression — and it makes your data bigger, not smaller. This guide covers what it actually does, when you need it, why Arabic and emoji come out broken in so many tools, and how the URL-safe alphabet differs.
Barcode Generator: Code 128, EAN-13, UPC-A and the Check Digit That Protects You From Errors
A barcode for stock, for a product shelf or for tracking parcels. This guide explains the four types, when to choose each, how the check digit works, and why drawing lines that look right is not enough for a product sold in shops.
How to crop excess PDF margins without cutting off content
You open a scanned PDF and find huge white margins around a small block of content in the middle, making it tiring to read on a phone and wasteful to print. This guide explains how to crop excess margins precisely without cutting into the text or table itself.
How to reduce a PDF file size without losing quality
A ten-megabyte PDF gets rejected by a CV upload system that only accepts five. Compressing a PDF solves this, but picking the wrong compression level either wrecks image quality or barely shrinks the file. This guide explains when to use each level and why compression doesn't work the same on every file.
How to Generate a Strong Password That Never Leaves Your Device
A password generator that round-trips through a remote server may have handed your password to that server the instant it created it. This guide explains why generating a password locally on your own device matters, and how to read its strength in bits of entropy instead of a vague verdict like "very strong."
Writing an Amount in Arabic Words Correctly for a Cheque or Invoice
Writing a figure out in words on a cheque or invoice sounds simple until Arabic number grammar breaks the pattern you expect: three riyals but three halalas differ in gender in the same sentence. This guide explains why an Arabic number agrees with the word it counts, and how to get a correct spelling without memorizing the rules.
Why a Flat-Rate Loan Costs More Than the Number on the Offer
Two finance offers arrive: one on a reducing balance, the other on a flat rate that looks like a smaller number. You pick the smaller number assuming it is cheaper, but a flat rate is calculated in a completely different way that makes its real cost much higher than the printed figure suggests. This guide explains the difference and converts both offers into one comparable number.
How to combine multiple images into one PDF, in the right order
You photographed ten ID documents and certificates with your phone camera, and need to send them as one file instead of ten scattered attachments. Turning images into a PDF solves this, but image order, page size, and orientation are details people get wrong all the time if you are not careful before combining. This guide explains how to get one organized file right on the first try.
Trimming Audio Clips Precisely Without a Click at the Cut Point
Quick-trim tools copy the file as-is without re-encoding, producing a click or glitch at the cut point because a compressed format's frames rarely align exactly with the moment you want. This guide explains the difference, and how to get a clean cut at both ends.
Changing Audio Speed From 0.5x to 2x Without Shifting Its Pitch
Speeding up audio the ordinary way raises its pitch until it sounds comical or unintelligible, and slowing it down lowers it until it sounds heavy. This difference between "faster" and "higher-pitched" is what time-stretching solves, and this guide explains how and why.
Loudness Normalization vs. a Simple Volume Boost
A simple volume boost only amplifies a file's loudest point, leaving quiet parts just as quiet as before. Loudness normalization measures the clip's overall loudness and adjusts it as a whole to a standard target, so it's heard at consistent clarity from start to finish. This guide explains the difference and why it matters.
Merging Multiple Audio Files of Different Formats Into One
Merging two audio files sounds simple until their formats differ — MP3 with WAV, say — and most basic tools refuse the merge or produce a broken result. This guide explains why, and how Sahel's tool handles any mix of formats in the order you choose.
Converting Audio Between MP3, WAV, OGG and M4A: Which One and When
Four audio formats that look interchangeable are actually built for different jobs: MP3 for wide compatibility, WAV uncompressed for editing, open-source OGG, and M4A for Apple devices. This guide explains when each format actually matters, and why converting an already-compressed file to another format never restores lost quality.
How to Calculate the Share of Each Heir in an Islamic Estate
Dividing an estate is not simple arithmetic — it depends on exactly who survived from each degree of kinship, and who was excluded because someone closer did. This guide explains how an inheritance calculator works out shares the way a court writes them, and why it deliberately stops at certain cases instead of guessing.