How to Compress a PDF on iPhone Before You Email or Message It
It always happens away from your desk: the landlord wants the signed lease now, the scanned PDF on your iPhone is 32 MB, and the email bounces back or the messaging app refuses the attachment. Mail can offer to shrink images, but for a PDF attachment iOS gives you no real compression option at all. The Files app can view, rename, and share PDFs, yet nowhere in the share sheet will you find a button that simply makes the file smaller.
The fix does not require an app store detour. Open Safari, go to PdfWill's compress tool, and pick the PDF straight from the Files picker, whether it lives in iCloud Drive, On My iPhone, or a folder synced from elsewhere. The compression itself runs inside Safari on your phone's own processor. That distinction matters on mobile more than anywhere: you are often on cellular data, so not uploading a 32 MB file to some server both protects the document and spares your data plan. Only the finished, smaller file touches your storage.
What the tool actually does is worth understanding in one sentence: it recompresses the images embedded in the PDF, which carry almost all the bulk, while leaving the text layer intact, so the output remains sharp, selectable, and searchable rather than turning into a blurry picture of a document. Scanned files respond especially well, because a phone-scanned page is essentially one large photo per page. A 30 MB scan dropping under 5 MB is a normal outcome, not a lucky one.
A few mobile-specific tips help. If the recipient only needs two pages of a long document, use split first and compress just the excerpt; a smaller input means a faster job and a friendlier attachment. If you are assembling a document from camera photos, run them through Image to PDF and then compress the result, which routinely beats sending four photos separately. When the download finishes, iOS places it in Files, and the share sheet takes it straight into Mail, WeChat, or WhatsApp.
Set expectations honestly: a phone browser is working with phone memory, so a 400-page scanned tome may push an older iPhone harder than it would a laptop, and text-only PDFs will not shrink much because there is little image weight to remove. For the common case, though, a scan or report that needs to slip under an attachment limit in the next five minutes, your iPhone plus its browser is a complete solution. No install, no account, no upload, and no excuse to wait until you are back at a computer.