PDF Compression Benchmark: How Much Can You Actually Shrink a PDF?
Real data from testing 6 document types — not generic advice
By Ben Praveen J · March 23, 2026
Most PDF compression guides say "compress your PDF to make it smaller" without telling you how much smaller. That is not helpful when you need to get a 45 MB scanned contract under Gmail's 25 MB limit, or shrink a portfolio below a job application's 10 MB cap. You need actual numbers.
We tested 6 common types of PDF documents through our free PDF compressor and recorded the exact results. Here is what we found.
Test Methodology
We selected 6 PDF documents representing the most common real-world scenarios. Each document was compressed using GoToolsOnline's PDF compression tool with default settings. We measured original file size, compressed file size, percentage reduction, and processing time. All tests were run on a standard server configuration with no special optimization flags — the same experience any user gets.
The Results
| Document Type | Pages | Original | Compressed | Reduction | Time |
|---|
| Text-only academic paper | 20 | 2.1 MB | 1.7 MB | 19% | 1.2s |
| Scanned contract (300 DPI) | 15 | 45 MB | 8.2 MB | 82% | 6.8s |
| Presentation export (charts + photos) | 30 | 28 MB | 9.4 MB | 66% | 4.3s |
| Photo-heavy portfolio | 10 | 85 MB | 22 MB | 74% | 9.1s |
| Government form (text + small graphics) | 5 | 3.8 MB | 1.4 MB | 63% | 0.9s |
| Invoice / receipt | 2 | 890 KB | 420 KB | 53% | 0.4s |
Analysis: Why Different PDFs Compress Differently
Scanned documents compress the most (82%). When you scan a paper document, the scanner creates a high-resolution image for each page — typically at 300 DPI, saved as an unoptimized JPEG or TIFF embedded inside the PDF. These images are the primary compression target. Our tool resamples them to a web-friendly resolution while keeping text readable, producing dramatic file size reductions. The 45 MB scanned contract dropped to 8.2 MB — well under Gmail's 25 MB attachment limit.
Photo-heavy documents compress significantly (74%). Portfolios, brochures, and marketing PDFs embed large photographs at high quality. Compression optimizes these images using efficient encoding without visible quality loss at normal viewing sizes. The 85 MB portfolio became 22 MB — small enough for most upload forms and email attachments.
Presentations compress well (66%). Exported slides typically contain a mix of charts, small photos, and text. The embedded images compress efficiently, while the text and vector graphics contribute minimally to the total size. Our 28 MB presentation deck dropped to 9.4 MB.
Government forms compress moderately (63%). These documents combine text, form fields, small logos, and background graphics. The graphics and embedded images compress, but the text and form structure is already efficient. Still, the reduction from 3.8 MB to 1.4 MB is meaningful for upload forms that cap at 2 or 5 MB.
Invoices compress reasonably (53%). Simple layouts with mostly text, a logo, and perhaps a table. Less image data means less to optimize, but the reduction from 890 KB to 420 KB still helps if you are attaching many invoices to a single email.
Text-only documents compress the least (19%). Pure text PDFs are already efficient — the text itself is stored as compact encoded characters, not pixels. Compression can optimize font data (subsetting removes unused glyphs) and internal PDF streams, but there are no large images to shrink. The 19% reduction still brings the file from 2.1 MB to 1.7 MB, but if you need a smaller text PDF, the document is likely already near its minimum practical size.
Tips for Maximum Compression
- Resize images before embedding. If you are creating a PDF from scratch, resize photos to the display size before inserting them. A 4000x3000 photo displayed at 800x600 in the PDF wastes space — resize it to 800x600 first, then insert.
- Use lower scan resolution when possible. 200 DPI is sufficient for most text documents. 300 DPI is only necessary when you need to preserve fine details or small print. Scanning at 150 DPI for internal-only documents can reduce size by 50% compared to 300 DPI.
- Split then compress for very large files. If your PDF exceeds 100 MB, use our PDF Split tool to break it into sections, then compress each section. This can produce better results than compressing the entire file at once.
- Compress after merging. If you combine multiple PDFs with PDF Merge, the merged file inherits all the original bloat. Run it through compression afterward for the best combined result.
- Remove unnecessary pages first. If your PDF contains pages you do not need (blank pages, cover sheets, appendices), use Split to extract only what you need before compressing.
When NOT to Compress a PDF
Compression is not always appropriate:
- Legal documents requiring exact byte-for-byte preservation. Some contracts, notarized documents, and court filings require the exact original file. Compression modifies the internal structure — even though the visible content is identical, the file is technically different. Check with your legal team before compressing documents that may be subject to integrity verification.
- Already-compressed PDFs. Running a previously compressed PDF through compression again yields diminishing returns — typically less than 5% additional reduction. If the first pass already achieved good results, a second pass is rarely worth the effort.
- Print-ready documents. If your PDF is going to a professional printer, they need the highest-quality embedded images. Compression reduces image quality slightly. Keep the original high-resolution version for print and create a compressed copy for screen sharing or email.
- PDFs with digital signatures. Compressing a digitally signed PDF invalidates the signature. The modification detection built into digital signatures will flag the file as altered, even though only the internal encoding changed.
Try it yourself: Compress your PDF free — no signup, no watermark, no daily limits. See your exact before/after file sizes instantly.
FAQ
- How much can you compress a PDF?
- It depends on content type. Scanned PDFs: 70-90% reduction. Image-heavy documents: 50-75%. Presentations: 50-70%. Text-only: 10-25%. Our benchmark table above shows exact results for 6 document types.
- Does PDF compression reduce quality?
- Text remains perfectly sharp — compression does not affect text rendering. Embedded images may show very slight softening that is imperceptible at normal viewing distance. For business documents, the quality difference is unnoticeable.
- Why do scanned PDFs compress so much more?
- Scanned PDFs are essentially high-resolution images wrapped in a PDF container. Scanners save at unnecessarily high quality by default. Compression optimizes these embedded images dramatically, often achieving 70-90% reduction while keeping text perfectly readable.
- Can I compress a PDF multiple times for better results?
- Yes, but with diminishing returns. The first compression yields the biggest savings. A second pass may squeeze out another 5-15%. Beyond that, further reduction is minimal. For the best results, compress once and verify the output meets your needs.
- How do I get a PDF under a specific size (like 1 MB or 5 MB)?
- Compress the PDF first and check the result. If it is still too large, consider: removing unnecessary pages with PDF Split, reducing the number of embedded images, or splitting the document into smaller sections. For more strategies, see our guide on reducing PDF size for email.
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