Quick answer
Open Compress PDF in Safari, pick the PDF from the Files app, choose a mode, and download the smaller file.
Step by step
- Open Safari (Chrome works too) and go to Compress PDF.
- Choose a mode. "Structure Only" suits text PDFs. "Rasterize & Recompress" saves the most on scans and photo-heavy files.
- Tap the drop area and choose the PDF from the Files app. If the PDF arrived by Mail or WhatsApp, tap Share and choose "Save to Files" first.
- Look at the size comparison, then tap the download button.
- Safari shows a download icon next to the address bar. Tap it to find the file, which is saved in the Downloads folder of the Files app. From there, tap Share to send it by Mail or WhatsApp.
Tips
- Documents scanned with the Notes app are image-based, so "Rasterize & Recompress" usually saves the most.
- Close other heavy tabs before compressing a big file, so Safari has more memory to work with.
- Keep the original in Files. Rasterizing makes the text non-selectable.
Good to know
Nothing is installed and nothing is uploaded: the compression happens inside Safari on your iPhone.
Try it now: Compress PDF. Free, no signup, and your files stay in your browser.