Compress Scanned PDF Files
Scanned PDFs are the largest type of PDF document you typically encounter.
Runs locally in your browser
No server upload during processing
No server-side file retention
No watermark added
- Cost
- Free tier
- Sign-up
- Not required
- Processing
- Tool-specific
- Privacy
- Clearly disclosed
Add this PDF Compressor to your website
Drop the PDF Compressor into a blog post, product docs, intranet, or school portal with one iframe. Processing, privacy, and usage limits are the same as on the full tool page.
- One copy-ready line of HTML
- Responsive — adapts to any container width
- No API credentials are placed in the snippet
Embed code
<iframe
src="https://www.fixtools.io/pdf/pdf-compressor?embed=1"
width="100%"
height="780"
frameborder="0"
style="border:0;border-radius:16px;max-width:900px;"
title="PDF Compressor by FixTools"
loading="lazy"
allow="clipboard-write"
></iframe>Attribution-friendly: a small "Powered by FixTools" link appears in the embed footer.
Why scanned PDFs are so large and how DPI resampling fixes that
When a physical document is placed on a flatbed scanner or fed through a document feeder, the scanner's sensor captures reflected light as a pixel grid. The density of that grid is the dots per inch setting. Consumer and office scanners default to 300 DPI for documents, which produces 300 pixels per linear inch. An A4 page is approximately 11.7 inches tall and 8.3 inches wide, so a 300 DPI scan produces a raster image of 3,510 by 2,490 pixels, or about 8.7 megapixels per page. Even after JPEG encoding within the PDF container at quality 80, that single page weighs 500KB to 2MB. A 10-page scanned contract can easily reach 10 to 20MB. At 600 DPI, the default on some scanners for OCR accuracy, the same page is four times larger in pixel count and the file size scales proportionally.
The key insight is that 300 DPI is necessary for OCR accuracy and for producing clean printed output, but it far exceeds what any display device needs. A typical computer screen renders at 72 to 110 PPI. A Retina or 4K display at its native density reaches 220 to 260 PPI. An image displayed at 96 DPI on a 100 PPI screen is already rendering at near-native display density because every pixel in the image maps to approximately one pixel on screen. Storing the image at 300 DPI in a PDF that will only be read on screen wastes between ten and twenty times the image data. FixTools resamples embedded raster images from their original scanner DPI down to approximately 96 DPI, which is sufficient for all screen display purposes and for printing at standard office quality, because 600 DPI printers interpolate well from 96 DPI source images.
Greyscale and black-and-white scans compress more efficiently than colour scans because they contain less colour data per pixel. A greyscale scan at 300 DPI can reach 200 to 800KB per page. A black-and-white (monochrome) scan of a text page at 300 DPI may only be 50 to 200KB per page using CCITT Group 4 or JBIG2 encoding. Colour scans at 300 DPI are the largest because each pixel stores three colour channels of red, green, and blue. When compressing scanned PDFs, FixTools identifies each image stream's colour mode and applies the most efficient re-encoding: JPEG for colour and greyscale, more compact encoding for near-monochrome content. If your scanner produced a colour scan of a black-and-white document, switching the scanner to greyscale or monochrome for future scans will produce significantly smaller PDFs before any compression is needed.
It is worth understanding that compression on scanned content is fundamentally lossy in a way that does not affect digitally created PDFs. A native PDF stores text as vectors which can be re-rendered at any resolution without quality loss. A scanned PDF stores text as pixels, so when the image is downsampled, the visual representation of each character contains less detail. For body text at 10 to 12 point font scanned at 300 DPI, downsampling to 96 DPI leaves roughly four pixels per character stroke, which is enough for clear legibility on standard screens. For very small text, fine handwriting, or low-contrast print, the loss becomes visible. Inspecting the output at 150 percent zoom before sharing important documents is the simplest way to catch any problems early.
How to use this tool
Upload your scanned PDF and select high compression. Scanned documents have no vector text to protect, so high compression produces excellent results: typically 70 to 80 percent smaller with text remaining clearly legible at normal screen zoom.
How It Works
Step-by-step guide to compress scanned pdf files:
- 1
Open the PDF Compressor
Go to fixtools.io/pdf/pdf-compressor in your browser. No installation or sign-up needed and the page loads in under a second on a typical broadband connection.
- 2
Upload your scanned PDF
Drag the scanned PDF onto the upload area or use the file picker. Files at 300 DPI may be 10 to 50MB in size which is entirely expected for scanned content and well within the tool's capacity.
- 3
Select high compression
For scanned documents, high compression is appropriate because there is no vector text or fine line art to preserve at maximum quality. The raster images will be resampled to 96 DPI, which is sufficient for screen and office printing.
- 4
Compress and verify
Click Compress PDF. After downloading, zoom in on text in the output to confirm it remains legible. For typical printed text at 10pt or above, legibility is maintained, and any quality issues become obvious at 150 percent zoom.
- 5
Compare file sizes
Note the original and compressed sizes side by side. A 70 to 80 percent reduction is typical for colour scans, and a 20MB scanned PDF commonly compresses to between 4MB and 6MB depending on page count and visual density.
Real-world examples
Common situations where this approach makes a real difference:
A legal firm scans 200-page client case bundles at 300 DPI for digital filing in the matter management system. Each bundle is 180 to 220MB. Court portals cap uploads at 30MB per submission, so the originals are unusable for direct upload. After high compression in FixTools, each bundle reaches 35 to 45MB. Splitting into two parts and compressing each produces 18 to 22MB files that upload cleanly within the portal limit, allowing the firm to file electronically rather than couriering physical bundles.
A GP surgery scans patient registration forms (three pages each) at 300 DPI colour. Each form is 9 to 12MB. The practice management system has a 2MB per-document limit, which blocked the entire planned migration to paperless records. High compression reduces each form to 1.4 to 1.8MB. All text including handwritten patient signatures and notes remains readable at 150 percent zoom on the practice's 1080p monitors, and the records project resumes without a software change.
A council archiving officer scans 50 years of planning permission documents at 300 DPI for a digital repository. Single-page decisions average 2.5MB each, producing a 500-document archive of 1.25GB. Medium compression reduces the average to 550KB per page, shrinking the archive to 275MB and fitting it on a standard USB drive for off-site backup. The smaller archive also indexes and searches significantly faster inside the repository's OCR-based search interface.
A self-employed builder scans receipts for expenses on a smartphone app that defaults to 300 DPI colour. Each receipt scan is 3 to 5MB. His accountant's portal has a 1MB per-attachment limit which had previously meant rejecting his uploads. High compression in FixTools reduces each receipt to 200 to 400KB while keeping amounts and supplier names legible. The monthly expense submission, which used to take a frustrating hour of trial and error, now completes inside twenty minutes.
Pro tips
Get better results with these expert suggestions:
Switch your scanner to greyscale for text documents
If you are scanning text-only documents such as letters, contracts, and forms with no colour graphics, switching your scanner setting from colour to greyscale reduces the raw scan size by 66 percent before any compression. A colour scan at 300 DPI might be 3MB per page; the same page scanned in greyscale is typically 800KB to 1.2MB. Applying FixTools compression to a greyscale scan produces an even smaller final file because the starting point already discarded the unnecessary colour channels.
Check if your scanner has a built-in PDF compression setting
Many modern office scanners including Canon imageFORMULA, Fujitsu ScanSnap, and HP Enterprise scanners offer built-in PDF compression settings in their scan profiles. Enabling a medium compression profile at the scanner level can produce PDFs of 200 to 500KB per page without any post-processing. If your scanner already compresses output well, FixTools compression may offer smaller additional gains, but it remains useful as a finishing step when the scanner output still exceeds a portal limit.
High compression is appropriate for scanned text documents
Unlike digitally created PDFs where high compression risks degrading photographs, scanned text documents benefit from aggressive compression with minimal visible impact. The human eye tolerates JPEG artefacts in text images more than fine photographic detail at typical reading distances. For scanned forms, contracts, and letters, high compression in FixTools is the correct default choice, and it leaves the photograph-friendly low setting for documents that genuinely contain photographic content needing the highest possible fidelity.
Run OCR before compressing for searchable archives
If you need your scanned PDF to be text-searchable for example for a document management system, run OCR on the original high-resolution scan first, then compress the OCR-processed file. Compressing before OCR can degrade character recognition accuracy for small or unclear text because the OCR engine has fewer pixels to analyse. Once the OCR text layer is embedded, compression of the image layer does not affect the searchable text in any way.
Frequently asked questions
Related tools
Other tools you might find useful:
PDF Merger
Merge multiple PDFs after compressing each.
PDF Splitter
Split large PDFs before compressing.
Image Compressor
Compress images before embedding in PDF.
Compress PDF for Upload to Any Portal or System
Compress a PDF to fit any upload size limit. Free browser tool, check your current file size, pick a target, compress. Works for any portal, form, or system.
Compress PDF in Your Browser, No Upload Required
Compress PDF directly in your browser without uploading to any server. FixTools uses the FileReader and Canvas APIs so your file never leaves your device.
Shrink PDF File Size Online
Shrink PDF file size instantly in your browser. Free, no sign-up, no watermark. Same result as "compress PDF", FixTools reduces image DPI and strips metadata.
Compress PDF on Windows
Compress a PDF on Windows 10 or Windows 11 for free. Use FixTools in Chrome or Edge, no software to install. Compare with Adobe and iLovePDF for Windows.
Compress Multiple PDFs Online
Compress multiple PDFs for free in your browser. No batch upload needed, process each PDF in sequence with no daily limits. Faster than you think for 10-20 files.
Compress PDF on Mac
Compress a PDF on Mac for free. Compare macOS Preview's built-in compressor with FixTools browser-based tool. No download, no watermark, better results.
Ready to get started?
Open PDF Compressor to review its free limits and processing method.
Open PDF Compressor →Free tier · No account needed · Transparent limits