How to make a scanned PDF smaller on iPhone
You scanned a document, went to upload it, and the website said the file is too large. In iOS 26 you can make a smaller copy on the iPhone itself, with the Preview app.
Make a smaller copy with Preview
- Open the Preview app and open the scanned PDF.
- Tap the Actions menu button next to the file name, then tap Export.
- Choose PDF as the format.
- Apple's guide says you can then use a slider to adjust the file size. Move it towards the smaller end, finish the export and choose where to save the copy.
- Open the copy and make sure you can still read the smallest print on it.
Keep the original. If the copy is too blurry to read, export again with the slider set a little higher.
We haven't yet confirmed on a phone that the slider appears when PDF is the chosen format, as well as for image formats. If you don't see it, let us know.
If the scan is in Notes
Preview can only open files, so save the scan as a file first:
- Open the note and tap the Menu button on the scanned document itself (not the Share button at the top of the note).
- Tap Share, then Save to Files, and pick a folder.
- In Preview, tap Browse and open the file from that folder.
Check the size
In the Files app, touch and hold the PDF, then tap Get Info. The size is listed there. Compare it with the limit the website gives, and check again after each change.
If it's still too big
Upload it in parts. Many upload forms let you add more than one file. In Preview, make a copy with Duplicate in the Actions menu. In the copy, tap the page count to show the pages, touch and hold a page you don't want in this part, and tap Delete Page. Repeat until the copy holds only the pages for one upload. Make another copy for the next part. Check that every page ends up in one of the parts.
Remove pages nobody needs. A blank back side or a cover sheet adds size and nothing else. Delete it the same way.
If it's an email that won't send, rather than an upload, Mail may offer to send the file with Mail Drop, which gives the recipient a download link.
Two things that don't help
Compress in Files makes a ZIP, not a smaller PDF. Touching and holding a file in Files and tapping Compress makes a ZIP archive. If the form asks for a PDF, a ZIP won't do.
Sending camera photos instead usually doesn't solve it. Each photo can be as big as a scanned page or bigger, and the person on the other end gets a pile of images instead of one document.
Why scans get so big
The iPhone's scanner saves each page as a detailed image of the paper. We measured four scans made with the built-in iPhone scanner: each page came to between 0.45 MB and 1.1 MB. A one-page scan was 0.56 MB, a two-page scan 1.0 MB, and an eight-page scan 8.1 MB.
Those are four examples, not a rule, and your pages may come out differently. They do show why a short scan usually passes a 2 MB limit and a long one usually doesn't, and why a limit of 500 KB can be too small even for one page.
Where the built-in tools fall short
The Preview slider works by eye: you set it, check the size, and sometimes go round again before the file is under the limit. On a long document you may also have to split the PDF by hand to get each part under the limit.
Sources
Export or compress PDFs and images in Preview, Add, delete, rotate, move, or crop PDF pages in Preview, Save, rename, or move PDFs and images in Preview, Send files from the Files app and Work with PDFs in Notes, from Apple's iPhone User Guide for iOS 26.
These guides are written by the people building Paperfind, a document scanner for iPhone. It isn't out yet, so there is nothing to download. Everything in this guide works with apps already on your phone.