How to Compress a Scanned PDF on iPhone and Android

When you use your phone's camera or a scanning app to capture a document, the app typically saves the image at a high DPI (dots per inch) — often 200–300 DPI or higher. Each page is essentially a large photograph embedded in a PDF container. Unlike a digitally created PDF (from Word or a web page), a scanned PDF has no actual text layer — it's just images stacked together. This means a 10-page scanned report can easily be 30–80 MB because each page is a full-resolution image. Color scans are especially heavy. A color scan of an invoice at 300 DPI can be 4–5 MB per page. Even grayscale scans at 200 DPI run 1–2 MB per page. Compression works by reducing the image resolution (downsampling), applying efficient image compression algorithms like JPEG or flate, and removing redundant metadata. The goal is to find the right balance: small file, still readable.

1. 1Open your browser on iPhone or Android and go to LazyPDF's compress tool.
2. 2Tap 'Choose File' or drag your scanned PDF into the upload area.
3. 3The tool automatically applies optimal compression — images are downsampled and re-encoded.
4. 4Download the compressed PDF once processing is complete.
5. 5Compare file sizes: most scanned PDFs shrink by 60–85%.

On iPhone, the most common sources of scanned PDFs are the built-in Notes app, the Files app scanner, and third-party apps like Scanner Pro or Adobe Scan. These apps typically produce PDFs ranging from 2 MB to 15 MB per page depending on settings. Once you have the PDF in your Files app or Camera Roll, the easiest compression method requires no extra app installation. Open Safari or Chrome on your iPhone, navigate to LazyPDF.com, and use the compress tool directly in your browser. The entire process — upload, compress, download — happens in under a minute for most documents. After downloading the compressed file, iOS will save it to your Files app. You can then share directly from there via email, AirDrop, or any other app. For recurring workflows, consider saving LazyPDF.com to your Home Screen as a Progressive Web App for one-tap access. If you need to compress many scans regularly, you can batch-process by combining pages first and then compressing the merged PDF in a single operation.

Android users have slightly more flexibility because the file system is more accessible. However, the built-in Android tools offer limited PDF compression options. Most scanner apps (Google Drive, Microsoft Lens, CamScanner) let you choose quality when scanning — but if you've already scanned at high quality, you'll need a post-processing step. The browser-based approach works just as well on Android as on iPhone. Open Chrome, navigate to LazyPDF.com, upload your scanned PDF, and download the compressed version. On Android, files download to your Downloads folder automatically. For power users, Android's Share sheet integration makes this even faster: you can share a PDF from any app (Google Drive, Files by Google, your email client) directly to the browser or a compatible app that performs compression. Some launchers and file managers also support compression plugins, but the web-based approach is more universal and requires no permissions. A practical tip for Android users: in Google Drive's scanner, setting quality to 'Normal' instead of 'High' before scanning can cut file size by 50% before you even need to compress.

Compression ratios for scanned PDFs vary significantly based on the source material, original resolution, and color depth. Here are typical results you can expect: **Black-and-white text scans**: These compress the most aggressively. A 10 MB text-only scan can often be reduced to 1–2 MB (80–90% reduction) while remaining fully readable. **Color document scans**: More complex images compress less dramatically but still significantly. A 20 MB color scan typically compresses to 4–8 MB (60–75% reduction). **Photo-heavy scans**: Pages containing many photographs or graphics compress less because the image data is inherently complex. Expect 40–60% reduction. **Post-OCR PDFs**: If OCR has been applied to create a text layer, compression is slightly less aggressive because the tool needs to preserve the text layer alignment. Still, 50–70% reduction is common. The key metric to aim for is file size per page: most business documents work well at 100–300 KB per page, which is a fraction of the typical scanned output.

One concern users have when compressing scanned PDFs is legibility. Nobody wants to submit a compressed scan where the text is blurry or signatures are unrecognizable. The good news is that most compression algorithms preserve legibility even at high compression ratios, because the human eye is more forgiving of subtle quality loss in documents than in photographs. For legal or official documents (contracts, court filings, medical records), aim for a compressed file that's under 2 MB per page while keeping text sharply legible at 100% zoom. If a compressed version looks good at 100% on your screen, it will print acceptably and be accepted by most online submission portals. For internal documents, presentations, or casual sharing, more aggressive compression is fine. A 95% size reduction is achievable for typical office documents without visible quality loss to most viewers. Always keep the original scan as a backup before compressing. Store the high-res original in cold storage and use the compressed version for sharing and distribution.