Many PDFs that need compressing are exactly the ones you would rather keep to yourself: ID scans, payslips, medical letters, contracts. Most online compressors work by uploading the file to their servers, processing it there and letting you download the result.
What happens with online compressors
The big web tools are open about this. Smallpdf describes its tools as cloud-based and says files are deleted after one hour. iLovePDF says processed files are deleted within two hours. PDF24’s web tools run on its servers in Germany and delete files after an hour. Adobe’s online compress tool processes the file on Adobe’s servers. Several of these services also state security certifications such as ISO/IEC 27001.
That can be perfectly acceptable. But it means your document leaves your device, if only briefly, and you rely on the service’s own handling. If your organisation’s rules or your own comfort say a document must not be uploaded, you need a tool that works locally.
On-device compression on Android
PDFTuck compresses the PDF on your phone:
- The file is picked through Android’s own file picker, so the app only sees the document you choose. It needs no storage permission.
- Compressing, previewing and saving all work with no internet connection. You can switch on airplane mode and compress.
- The PDF is not uploaded to PDFTuck or to any compression server. There is no account to create.
- Working copies stay in the app’s private storage and are deleted automatically. Your original file is never changed.
What still uses the internet
Being precise matters here. PDFTuck is free and shows Google ads, and where the law requires it, Google’s consent tool asks for your choice. These Google services use the internet and collect advertising data such as device identifiers, as disclosed in the app’s privacy policy and Google Play data safety section. PDFTuck does not give them your PDF, its contents, its name, your target size or the result.
So “nothing leaves your phone” would be wrong about the app as a whole. “Your PDF never leaves your phone for compression” is right.
Steps
- Optional: turn on airplane mode, to see for yourself that no connection is needed.
- Open PDFTuck, tap Select PDF and choose the file.
- Choose a target size (200 KB to 10 MB presets, or a custom value) or a quality mode.
- Tap Compress PDF, check the preview and save.
Other local options
On a computer, desktop software such as PDF24 Creator (Windows) or Adobe Acrobat’s desktop app can reduce file size locally, and iLovePDF’s desktop app offers offline processing on its paid plan. If you work mainly on a computer, those can be good choices with far more features than PDFTuck.