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Reduce file size without losing quality.
Scanned PDFs are often huge because they consist of images. Whether you have old book scans, archived papers, or scanned forms, our free online tool compresses scanned PDFs efficiently – keeping text readable, preserving quality, and reducing file size. No sign-up, no software – just upload, compress, and download.
Did you know? A 300 DPI scanned colour page can be over 5 MB. A 100‑page book scan can exceed 500 MB. Our compression can reduce scanned PDFs by 70‑90%, making them easy to share and store.
Scanned documents are essentially raster images: each page is a picture. This means the file size depends on resolution (DPI), colour depth, and number of pages. Unlike text‑based PDFs, which are small because they store text as vector data, scanned PDFs store every pixel, leading to huge file sizes.
Here are the key reasons why scanned PDFs are large and how our tool tackles them:
Scanning at 300 DPI or higher creates massive files. Our tool downsamples images to a reasonable DPI (150‑200) without losing readability.
Colour scans are much larger than black‑and‑white. Converting to grayscale or black‑and‑white can cut file size by 30‑60% with little impact on readability.
A 50‑page scan is simply 50 images. Compression reduces the size of each page, resulting in a much smaller overall file.
Scanners often add extra metadata that bloats the file. Our tool removes redundant metadata to save space.
Understanding the impact of DPI on file size helps you choose the right scanning settings and compression level. Here is a typical comparison for an A4 page:
Our tool can reduce DPI and apply grayscale conversion automatically, giving you the best balance between file size and readability.
Our tool uses a multi‑step approach to compress scanned documents efficiently:
The result is a scanned PDF that is much smaller but still clear and usable for archiving, sharing, or further processing.
Compression reduces file size while keeping your scanned content readable. Our tool uses smart algorithms to optimise images and data, making your scanned PDF manageable.
DonePDF Compress PDF in your browser (Chrome, Safari, Edge, Firefox).
Upload your scanned PDF from device, cloud, or drag & drop.
Choose compression level – “Standard” for high quality, “Maximum” for smallest size.
Click “Compress” – processing takes seconds.
Download the compressed PDF and share or archive it easily.
Free tier: 3 compressions/day, up to 50 MB. For larger files, paid plans support batch processing and higher limits.
Our tool offers three compression modes tailored to scanned documents. Here is a quick comparison:
For most scanned documents, “High” compression offers an excellent balance of size and readability. If you need maximum storage savings, use “Maximum”.
You might consider these alternatives, but they come with drawbacks:
Our online compressor is free, works everywhere, and handles multi‑page scanned documents in seconds.
Pro Tip: If you scan many documents regularly, consider scanning at 150 DPI in grayscale to keep files small from the start. Our tool can still compress further if needed.
Reduce scanned PDFs by 70‑90%, making them easy to share and store.
Text remains clear and readable even after aggressive compression.
Process files in seconds with full encryption and auto-deletion.
Use the tool instantly – no registration needed.
⚡ Need even smaller files for massive scanned documents?
Our Hyper Compress PDF tool applies aggressive downsampling and grayscale conversion – perfect for very large book scans and archives. Try it for extreme compression.
Scanned PDFs are essentially images – each page is a high‑resolution picture. A typical A4 page scanned at 300 DPI can be 2‑5 MB, and a 50‑page document can exceed 100 MB. Our tool reduces file size significantly while keeping content readable.
Our smart compression preserves text clarity. We use advanced algorithms that reduce image size while maintaining legibility. For best results, use “High” or “Maximum” compression – the text will still be readable, and you can further apply OCR for searchability.
Yes, “Standard” compression reduces file size without any quality loss by removing metadata and optimising streams. For scanned images, “High” compression offers a good balance, and “Maximum” is best when size matters more than absolute quality.
Absolutely. We use TLS encryption and auto-delete all uploaded files within 2 hours. Your sensitive scanned documents are never shared or stored.
If the file remains large, try “Maximum” compression or use our Hyper Compress tool. You can also reduce the DPI before scanning (e.g., 150 DPI for archival). Our tool can downsample images to reduce size significantly.
Yes, our tool works with multi‑page scanned PDFs. It processes all pages and applies compression to each, reducing the overall file size while keeping every page readable.
Upload your scanned PDF and compress it in seconds – free, secure, and ready for archiving or sharing.
Scanned documents are essentially images – each page is a high‑resolution picture. This makes them significantly larger than text‑based PDFs. Our tool downsamples these images and applies efficient compression, reducing file size while keeping text readable.
For scanned PDFs, use "Maximum" compression with grayscale conversion. This can reduce file size by 70‑90% while maintaining readability. If you need searchable text, run OCR after compression – the text layer is small and does not affect file size significantly.
OCR adds a hidden text layer to scanned PDFs, making them searchable without increasing file size noticeably. For best results, compress first (to reduce the image size), then run OCR to add searchable text. This gives you a small, searchable, readable document.
Explore the full collection of tools in the PDF Size Problems.