Guides & tips for working with PDFs
Practical how-tos, behind-the-scenes notes, and product updates from the team behind Blackpdf.
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OCR, repair, compare, grayscale, enhance scans, and PDF/A.
How to Find Changes Between Two Versions of a Document
Someone sent back a 'lightly edited' contract and you need to find every change. Here's how to compare two PDF versions and catch the edits you'd never spot by eye.
How to OCR a PDF in Another Language
OCR fails badly when it's set to the wrong language. Here's why the setting matters so much, which languages are supported, and what to do with a multilingual document.
How to Extract Text from a Scanned PDF
Can't select or copy the text in a PDF? It's a scan — an image of words, not words. Here's how OCR turns it into text you can search, copy, and edit.
How to Enhance a Faded or Low-Contrast Document
Old receipts, faded carbon copies, and pale pencil notes scan badly. Here's how to bring the text back without the whitening step erasing the very content you're trying to save.
How to Clean Up a Scan Before OCR (For Better Accuracy)
OCR accuracy depends almost entirely on the quality of the image you feed it. Here's how to prepare a scan so the text recognition actually works — and the order that matters.
How to Enhance a Whole Batch of Scanned PDFs
Cleaning up a stack of scans one at a time is a waste of an afternoon. Here's how to process them together — and when a single set of settings works for all of them.
"PDF Version Not Supported" — How to Fix a Rejected Upload
An upload portal rejected your PDF over its version number. Here's what that means, why it happens, and how to fix it in seconds without touching your document's content.
How to Make a PDF Open in Older Software and Printers
A PDF that won't open on an old reader, or crashes a print shop's machine, is often a version problem. Here's how downgrading fixes it without touching your content.
How to Convert a PDF to PDF/A
Convert a PDF into an archival PDF/A file. How to choose between PDF/A-1, 2, and 3, what the a/b/u conformance letters mean, and which colour profile to pick.
How to Automate Repetitive PDF Tasks with Workflows
Chain PDF operations into a saved workflow — unlock, OCR, compress, watermark, number — and run the whole sequence on new files in one click instead of repeating it by hand.
How to Remove a Shadow from a Scanned PDF
Got a shadow or grey gradient across a scanned page? Here's why it happens, how to remove it with the Whiten Background control, and how to keep faint content from disappearing too.
How to Scan a Document with Your Phone (and Make It Look Like a Real Scan)
Your phone is a scanner — if you shoot and clean up the photo the right way. The full workflow: capture, straighten, enhance to a flat white background, OCR, and combine into one PDF.
How-ToHow to Enhance a Scanned PDF (Clean Up Photos of Documents)
Turn a phone photo or a grey, shadowed scan into a clean PDF with a flat white background. How the Whiten, Exposure, Contrast, and Sharpness controls work, and when to use each.
How-ToHow to Convert a PDF to Grayscale (Black & White)
Turn a colour PDF black and white for cheaper printing and smaller files. The four grayscale modes, what DPI to pick, and when grayscale beats compression.
How-ToHow to Repair a Corrupted PDF
Fix a PDF that won't open, shows errors, or displays blank pages. Step-by-step guide for diagnosing damage and recovering as much as possible.
How to Compare Two PDFs and Spot the Differences
Compare two versions of a PDF side by side, as an overlay, or as a highlighted difference view. Step-by-step guide for catching changes between revisions.
PDF Accessibility Explained: Tagged PDFs and PDF/UA
Why some PDFs work with screen readers and others don't, what tagged PDFs are, how PDF/UA differs from PDF/A, and what makes a PDF legally accessible.
How-ToHow to OCR a PDF (Make Scans Searchable)
Run OCR on a scanned PDF to make the text searchable, copyable, and screen-reader friendly. Step-by-step, plus how to pick the right language.
PDF Versions Explained: What 1.4, 1.7, and 2.0 Actually Mean
Every PDF carries a version number in its header — 1.3, 1.4, 1.7, 2.0. Here's what each version adds, which one a system will accept, and when to change it.
How to Change a PDF's Version (1.3, 1.4, 1.7, 2.0)
Step-by-step guide to changing a PDF's version header — when you need to, which target to pick, and how the lossless rewrite works.
GuidesPDF vs PDF/A: Which One Should You Use?
PDF vs PDF/A explained: what the archival format changes, when courts and regulators require it, and when standard PDF is the better everyday choice.