Compress PDF

A scan and a typed report are both PDFs, but there is nothing alike about the way they need to be compressed. So your file is checked first, then handled to suit.

A document with real text, like an invoice or a contract, is compressed structurally. Unused objects are dropped and every stream is packed tighter. Your words, fonts, and links are left alone. The saving is real but modest, because a well-made text PDF is already efficient.

A scan has no text to protect. Its pages are already pictures, so they are re-encoded at the resolution your level sets. That is where the big reductions come from, and it is why the level matters on a scan and changes nothing on a text file. If you want a scan searchable as well as smaller, run it through OCR PDF first, then compress it.

Some numbers from our own testing, on a slow two-core machine. A 22-page text document with a few hundred images went from 1.58 MB to 1.35 MB at Standard, about 15 per cent, in under half a second. A 15-page scanned catalogue came down by roughly 85 per cent at the same setting. Your file and your device decide where you land between those two.

The three levels are named after where the file is going. Each one sets the resolution used when pages are re-encoded as pictures.

• Highest quality. Pages at 144 dpi. For anything that will be printed, or where small text on a scan has to stay readable.
• Standard. Pages at 108 dpi. Selected for you, clear on any screen, and right for most files.
• Smallest file. Pages at 72 dpi. For email and upload forms, where a slightly softer scan costs you nothing.

None of the three turns text into pictures by itself, so a text document gives you the same file whichever you pick. The panel shows the real size of each level, measured by actually making that file, not guessed at from a multiplier.

If a text document is still too big, tick Make it much smaller, text becomes pictures in the panel. Its pages are then re-encoded at the level you chose, the file gets far smaller, and the text stops being selectable, searchable, or readable aloud. The box is off unless you tick it. One thing worth knowing: on an ordinary text page, pictures at 144 or 108 dpi often come out larger than the original, so those levels keep the lossless copy instead and say so on the line. On a 22-page document we tested, only 72 dpi won, at about 40 per cent off.

Leave it on Standard, and leave the box alone, if you are not sure.

If your PDF asks for a password to open, this tool asks you for it too. Type it in, tap Unlock, and the file is unlocked on your device before it is compressed. Your password stays on your device, the same as the file does. If you would rather take the password off the document for good, use Unlock PDF first, then compress the copy.

Drop more than one file and each is compressed in turn on your device. One level applies to the whole run, and every finished file gets its own download button showing what it saved. Download all as ZIP collects them together. Change the level after a run and a Run all again at this level button appears, so trying a different setting does not mean adding your files again.

The same opt-in is there as Text may become pictures, and it applies to every file in the run. A file that cannot be made smaller is marked as such and passed through untouched, so nothing in a batch comes back worse than it went in.

Yes. Many free PDF compressors upload your file to their servers and delete it an hour or two later. This one never sends it anywhere, so it is a safe choice for payslips, medical records, signed contracts, and anything else you would not want sitting on a stranger's server.

It also means the tool keeps working with no internet once the page has loaded. Switch off your Wi-Fi and compress a file, and you can see for yourself that nothing is being uploaded.

Usually because it was already well built, and there was nothing left to strip out. The other way to make it much smaller is to turn every page into a picture. The number looks better and the document stops being a document: text cannot be selected, searched, or read aloud, and it prints worse. That is never done to a file with real text in it unless you tick the box asking for it, and the box says what you are giving up.

If it is still too large, take out pages you do not need with Remove Pages, break it up with Split PDF, or drop the colour with Grayscale PDF if it is going to be printed in black and white anyway.

Here is the breakdown, so nothing about the file you get back is a surprise:

• Every page, in the same order, at the same page size.
• Real text, still selectable, searchable, and readable by a screen reader, unless you tick the box that turns pages into pictures.
• Fonts, links, and page structure on a text document.
• Sharpness on scanned pages, which drops to the dpi of the level you chose. That is the one trade you are making.
• A guaranteed saving. If the file cannot be improved, you are told and your original is kept.

This tool does not make PDF/A archive files. If a submission asks for PDF/A, compressing here will not give you one.

Most mail services stop at around 20 to 25 MB, and bank or government upload forms are often stricter, sometimes 2 MB or 5 MB. If a scan is what is pushing you over, Smallest file gets you under fastest. If a text document is still too large, the weight is in the images inside it, and cutting pages you do not need usually beats compressing harder.

Try Standard first, check the new size, and only drop to Smallest file if you still need to.

Yes. It works in mobile Safari, Chrome, and other modern mobile browsers, with nothing to install. On a narrow screen the compression panel opens from the Compression options button instead of sitting next to your document, so the page you just added stays visible. How long it takes depends on your phone and your file, and a large scan will take longer on a phone than on a laptop.

• Getting a scanned application under a government portal's upload limit.
• Shrinking a photo-heavy report before emailing it to a client.
• Cutting down a batch of scanned invoices before filing them for the month.
• Making a signed contract small enough for a form that rejects large files.
• Trimming a presentation exported to PDF so it is quicker to share.