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Guides

Short, practical reading about PDFs and paper: how to do things, why they work the way they do, and a few things to play with.

Tutorials

Step-by-step help for the jobs people actually search for.

TutorialHow to merge PDFs without uploading them anywhereCombine a contract, its annexes and a scanned signature page into one file, in the right order, without sending any of it to a server.TutorialHow to sign a PDF on your phone in under a minuteSomeone sent you a PDF to "sign and return". You don't have a printer, and you'd rather not install an app for one document.TutorialScanning paper with your phone: how to get clean, readable PDFsPhone cameras are better than most office scanners now. The problem is almost never the camera. It's the light, the angle and the table.TutorialWhy your PDF is so big, and how to make it smallerA 40-page report weighs 300 KB. A three-page scan weighs 28 MB. The difference isn't the number of pages, it's what's on them.TutorialHow to fill in a PDF form, even one that isn't fillableSome PDF forms let you click into the boxes. Others are just pictures of boxes. Here is how to handle both without printing anything.TutorialGetting rid of blank pages in scanned PDFsYou fed a stack of single-sided letters through a duplex scanner and now every second page is empty. Deleting them by hand is tedious; it doesn't have to be.TutorialHow to print a PDF as a bookletFold a stack of A4 sheets in half, staple the spine, and the pages read in order. Getting there takes one setting, if you know which one.TutorialDouble-sided printing on a printer that can't do itPlenty of home printers only print on one side. You can still print double-sided: print the odd pages, turn the stack over, print the even pages.TutorialTurning iPhone photos (HEIC) into a PDFYou photographed a receipt, an ID card or a whiteboard. Now a form wants a PDF, and the files on your computer end in .heic.TutorialHow to copy text out of a PDF (and why it sometimes comes out empty)Sometimes copying from a PDF works perfectly. Sometimes you get nothing, or one long line of words in a strange order. Here's why, and what to do about it.TutorialHow to watermark a PDF without ruining itA good watermark tells people the status of a document without making it unreadable. Most bad watermarks fail on size, opacity or placement.TutorialHow to split a long PDF into chaptersA 300-page manual is fine to keep, awful to email. Split it into chapters and send only the part people need.TutorialPosting a PDF on Instagram or LinkedIn: turn pages into imagesInstagram doesn't accept PDFs at all. LinkedIn does, but images often look better. Either way, you'll want each page as a crisp picture.TutorialWhat your PDF says about you: remove metadata before you share itEvery PDF carries a small identity card: who made it, with what, and when. Sometimes that card says more than the document itself.TutorialHow to compress a PDF so it's small enough to emailGmail caps attachments at 25MB, Outlook at 20MB. A scanned PDF blows past that in a handful of pages. Here's how to shrink it without retyping anything.TutorialHow to password protect a PDF (and what the password actually protects)Payslips, contracts, medical results: some PDFs shouldn't open for just anyone. Here's how PDF passwords actually work, and what they don't do.TutorialYour PDF keeps rotating back to sideways: the actual fixYou rotate it, close the file, and it's sideways again. It's not a bug in your reader; the file itself never changed. Here's what's actually happening.TutorialHow to convert a PDF to JPG images (and photos back to a PDF)Dropping a page into a slide, posting it online, or running it through something that only accepts images: here's how the conversion works both ways.TutorialHow to add page numbers to a PDFA report, a manuscript, a bundle of exhibits for a filing: each wants numbers placed differently. Here's how to add them, and when you actually need something else.

Explainers

How PDFs, paper sizes and signatures work, in plain words.

ExplainerA short history of the PDF, from a memo to an ISO standardThe PDF started as an internal project at Adobe with a modest goal: send a document to any computer and have it look the same. Thirty years later it's everywhere.ExplainerPDF/A, PDF/X and PDF/UA: what the letters meanA court asks for PDF/A, a print shop wants PDF/X, an accessibility audit mentions PDF/UA. They're all PDFs, each with a stricter set of rules.ExplainerA4 vs Letter, and why the A sizes fit together so neatlyMost of the world prints on A4. The United States and Canada print on Letter. The two are close enough to be confused and different enough to cut off your footer.ExplainerAre online PDF converters safe to use?It depends on what happens to your file after you click "upload". Some services are careful. Some are vague. A few tools never receive the file at all.ExplainerWhy can't I just edit this PDF?You want to fix one typo, and the PDF won't let you. It isn't being difficult on purpose. A PDF is closer to a printout than to a document.Explainer72, 150 or 300 dpi? Resolution explained for PDFs and imagesWhen you convert a PDF to images, or scan a page, you're asked for a resolution. Pick too low and text is fuzzy; too high and files balloon for nothing.ExplainerElectronic signature or digital signature: what's the difference?The words are used interchangeably, and they shouldn't be. One is a mark that shows intent. The other is a cryptographic seal that proves the file hasn't changed.ExplainerMaking accessible PDFs: a practical checklistA PDF that looks fine can be unusable for someone with a screen reader. Most of the fixes happen in the software you write in, before the PDF exists.ExplainerBates numbering explained, with examplesLaw firms, auditors and medical records teams stamp every page with numbers like ABC000123. Here's what that is, why it exists, and how to do it.ExplainerThe best free PDF tools in 2026, and when a paid one is worth itDozens of sites promise free PDF tools. The real differences are where your file goes while it's processed, what the free tier actually allows, and what each one simply can't do.

Play

A quiz, a game and a calculator, for a coffee break.

?PlayThe PDF quiz: ten questions for people who live in documentsPoints, paper sizes, standards and a bit of history. Ten questions, explanations after each answer, no sign-up, no email at the end.A4PlayGuess the paper size: a little game for your eyesA sheet appears, drawn to scale. Is it A4 or Letter? A5 or a postcard? Ten rounds. It's harder than it sounds.mmPlayPaper size calculator: every common size in mm, inches, points and pixelsA, B and C sizes, US paper sizes, envelopes and cards, with the pixel size at the resolution you choose. Handy when a form asks for an image of exactly one page.