You've been sent a PDF. Now what? The reassuring answer, on every device made in the last decade, is: just open it. PDF became the universal document format precisely because reading one requires nothing — no purchase, no install, no account. But "it just opens" hides a handful of differences worth knowing: which app will open it, whether that app is any good, and what to do on the occasions when opening is a problem.
Here's the tour, device by device, followed by the four failures people actually hit — and the fix for each.
Opening a PDF on Windows
Windows ships with Microsoft Edge, and Edge is a full-featured PDF reader: double-click a PDF and it opens in a tab, with a table of contents sidebar, search, annotation, and reading aloud. If another app has claimed the file — an old trial of some PDF suite, say — right-click the file, choose Open with → Edge, and tick "Always use this app" to make it the default.
The classic Adobe Reader still exists as a free download for those who want it, but for reading, the built-in option is genuinely sufficient — and it's one fewer installer keeping itself updated.
On a Mac
macOS handles PDFs through Preview, which remains one of the best PDF readers anywhere: fast, quiet, and capable of more than most people discover — highlighting, signing, page rearranging, and image export all live in it. Double-clicking a PDF opens Preview by default; the Markup toolbar in the preview pane also lets you annotate without opening the full app.
One Mac-specific nicety: Quick Look. Select a PDF in Finder and press the spacebar to preview it instantly — the fastest "what is this file?" check on any platform.
On iPhone and iPad
iOS and iPadOS open PDFs inline wherever they appear — Mail, Messages, Safari, Files — with a consistent viewer that supports search, annotation, and signing. Tapping a PDF attached to an email shows it right there; from Files, tapping opens it full-screen.
The useful habit on iOS is the Share sheet: any open PDF can be saved to Files, dropped into a note, sent elsewhere, or printed, from the same place. A PDF you need to keep should go into Files (iCloud Drive syncs it to your other devices); a PDF you just need to glance at can stay where it opened.
On Android
Android's built-in document previewer opens PDFs from Gmail, Messages, and the Files app — tap and it renders. For heavier reading, Chrome or Drive's viewer handle search and pagination well. As with Windows, if some long-forgotten app has claimed PDF duty and does it badly, clearing or changing the default in Settings restores sanity.
On Linux
Every desktop distribution ships a capable reader — the common ones are Evince (GNOME Documents, simply "Document Viewer") and Okular (KDE's reader, also installable elsewhere). Both handle search, forms, and annotation. And because the browser fallback is universal, any PDF also opens in Firefox or Chrome without ceremony.
"It opens, but something's wrong" — the four real failures
Almost every "I can't open this PDF" problem is one of these four, and each has a specific fix:
1. The pages are sideways. The rotation is saved into the file, so it opens sideways on every device, every time. Your viewer's rotate button fixes it only for that moment — close and reopen, and it's tilted again. The permanent fix is saving a new rotation into the PDF: How to Rotate a PDF Page (and Save It That Way) covers it.
2. It asks for a password. The document is encrypted, and the only way in is the password — from whoever sent it, or derived from your account if it's a bank statement or similar. If it's your own document and you're tired of typing it, How to Remove a Password From a PDF You Own removes the protection for good. If you never had the password, no viewer or tool can conjure it — that's what encryption means.
3. It opens, but there's no text — just pictures of pages. That's a scanned PDF: images, not text. It reads fine on screen, but search and copy do nothing. If you need those, the fix is a text layer: How to Make a Scanned PDF Searchable With OCR.
4. It won't open at all, or opens half-drawn. The file is damaged — truncated download, crashed save, dying disk. Re-download or re-request the file first; if the source copy is genuinely broken, Repair PDF attempts recovery on what's left.
Reading in the browser, working in the browser
Worth knowing, since you're reading this in a browser: modern browsers open local PDFs too — drag a PDF onto a new tab and it renders, entirely offline from the network's perspective. And the browser is where the rest of the PDF toolkit lives: viewing is the one thing every device does natively, but rotating a page permanently, removing a password, extracting a chapter, or making a scan searchable are jobs for tools, and all of them run in the same browser tab without installing anything. If the document needs more than reading, the toolkit is one page away.