Direct answer
The safest iPhone workflow is local: open the PDF, share it to PDF Shrink, pick the compression level, then export the result. This avoids uploading personal documents to a web service.
Recommended workflow
- Open the PDF from Files, Photos, Mail, or another app.
- Send it to PDF Shrink.
- Choose a compression level based on where the file will be shared.
- Save the smaller PDF back to Files or share it directly.
Which compression level should you use?
- Smaller: best when you still need crisp print quality.
- Balanced: best for everyday sharing.
- Extreme: best when email or web upload limits matter most.
Why iPhone-first?
Many PDF files start on the phone: Notes scans, camera scans, signed documents, downloads, and email attachments. Compressing locally avoids a round trip through a server.
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FAQ
Which compression level should I use on iPhone?
Use Smaller for crisp print quality, Balanced for everyday sharing, and Extreme when email or web upload limits matter most.
Does compressing a PDF on iPhone upload the file?
No. PDF Shrink compresses the PDF on device and requests no network access, so the file stays on your iPhone.
Can I compress scans from Notes or Files?
Yes. Send the PDF from Files, Mail, Notes exports, or another app into PDF Shrink, then save the smaller copy back to Files.