To compress a PDF without uploading it, use an app that does the work on your phone. In ProperPDF, open Compress PDF, pick the file, lower the image resolution and save a smaller copy. The file never leaves the device and the tool works offline. Compression is part of ProperPDF Pro on iPhone, iPad and Android.

Compress privately in four steps

  1. Open ProperPDF and tap Compress PDF.
  2. Select the PDF.
  3. Lower the image resolution until the estimated size is small enough.
  4. Save the copy, then zoom in on small text and signatures to check them.
Image resolution setting for PDF compression on Android
The Android compression screen lets you adjust image resolution. Check text and signatures in the saved copy. View full-size screenshot

Why not an online compressor?

Sites like Smallpdf and iLovePDF process your file on their servers. Smallpdf says it deletes uploads after one hour, and for most documents that's fine. For a payslip, a medical letter or a signed contract, skipping the upload removes the question.

If the file is still too big

Text-heavy PDFs have little to compress. Remove the pages the recipient doesn't need with Split PDF or Organize Pages, which cuts size without touching quality.

On iPhone, compression currently turns pages into images, so the copy loses selectable text, form fields and links. Keep the original if you need them.

Questions

Can I compress a PDF offline?

Yes. ProperPDF compresses PDFs on iPhone, iPad and Android without an internet connection.

Is it free?

No. Compress PDF is a Pro tool in ProperPDF.