Getting the most out of PDFs
How do I make a PDF smaller on my iPhone?
The Files app cannot change a PDF's file size. Open Compress PDF in Safari, pick the PDF from Files, choose Recommended or type the size limit you were given, and the smaller copy downloads to the Files app.
The PDF is too big to attach, or a website says it is over the upload limit, and all you have with you is your iPhone. The Files app can open, mark up and share a PDF, but it has no setting for file size. You do not have to wait until you are at a computer.
Make it smaller in Safari
- Make sure the PDF is in the Files app. If it is an email attachment, open it, tap the share button and choose Save to Files.
- In Safari, open Compress PDF, tap the upload panel and pick the PDF from Files.
- Choose a level, or To a size if you were given a limit. Both are explained below.
- Tap Compress PDF and wait a moment.
- Download the result. Safari saves it to the Downloads folder in Files, unless you have changed where Safari saves downloads. The name ends in -compressed, so your original is still there.
From Downloads you can attach it to an email, upload it to a form, or send it with the share button.
Which level to pick
- Recommended suits nearly everything you would send from a phone: email, messages and uploads. Pictures come down to about 150 DPI, which is clear on any screen and fine on an office printer.
- Light keeps pictures at about 300 DPI, for a file that will be printed properly.
- Strong goes to about 72 DPI for the smallest file. Photos soften visibly; text does not.
- To a size is for when a form or mail system names a number. Pick 100 KB, 200 KB, 500 KB or 1 MB, or type the limit in KB, and pictures are lowered step by step only until the file fits.
The size box counts 1 KB as 1,000 bytes. For a 5 MB limit type 5000, and for 10 MB type 10000. The result then fits whichever way the website counts a megabyte. For the most common form limit, Compress PDF to 2 MB opens already set.
Text and line art never lose quality, at any level. Only pictures, such as scans and photos, are made smaller.
Why PDFs made on a phone are so big
Most large PDFs on an iPhone started as photos. A page scanned with Notes or the Files app, or a photo saved as a PDF, is a full picture of the paper, and an iPhone camera records far more detail than a page of text needs. A few pages can run to several megabytes.
That spare detail is exactly what compression removes, which is why these files often shrink to a small fraction of their size with no difference you can see on screen.
A PDF exported from a typed document is different. It is mostly text, already small, and compression may barely change it. When that happens, the result screen says the file was already about as small as it gets.
If it is still too big
Send fewer pages. A portal that wants page 1 of a certificate does not need all twelve pages. Deleting a page on an iPhone or Android phone takes a minute in the browser, and the smaller document then compresses further.
Fit sparse pages onto fewer sheets. SmartShrink puts the content of mostly empty pages onto fewer pages, then compresses as well.
Send a link instead of the file. For email, Apple Mail can offer Mail Drop when an attachment is too large, which sends the recipient a download link instead.
Scan smaller next time
The iPhone's document scanner, in Notes and in the Files app, lets you pick how a page is captured before you save it: colour, greyscale, black and white, or photo. For letters, forms and statements, greyscale or black and white gives a cleaner page and a smaller file than colour, because a colour scan of black text on white paper stores colour information nobody needs. Keep colour for photos, stamps and anything where colour carries meaning.
Two more habits help. Let the scanner find the edges of the page so the desk around it is cropped away, and scan only the pages the form asks for. A smaller file at the start means less to take away later, and less risk of soft text.
Uploading the smaller copy to a website
When a form on a website asks for the file, tap its upload button in Safari and choose the file from the Downloads folder in Files. Look for the name ending in -compressed, so you send the small copy and not the original. If the website shows the file size after you choose it, check it is under the limit before you submit.
On an Android phone
The steps are the same in Chrome or any other browser: open Compress PDF, choose the PDF from your files, pick a level or a size, and download. The smaller copy goes to the Downloads folder.
Email has its own limits
Attachments grow by about a third on the way, because email has to encode them as text, and the receiving server's limit can be lower than yours. Why won't my PDF attach to an email? explains both, and why aiming for about three quarters of the stated limit saves a bounced message.
Where your file goes
The PDF is sent over an encrypted connection to our server, compressed there, and deleted after processing. There is no app to install and no account to create. The original in Files is never changed; the smaller version is a separate file.
Common questions
Can I compress a PDF on my iPhone without an app?
Yes. Open Compress PDF in Safari, pick the PDF from the Files app, choose a level and download the smaller copy. It goes to the Downloads folder in Files.
Which level should I use for email?
Recommended. Pictures come down to about 150 DPI, which is clear on screen and prints fine, and text stays sharp.
How do I get under an exact limit, like 10 MB?
Choose To a size and type 10000 in the KB box. The file is made smaller step by step until it fits, and you are told if it cannot get that small.
Why did my PDF hardly shrink?
It is probably mostly text, which is already compact. Remove pages you do not need, or use SmartShrink to fit sparse pages onto fewer sheets.