PDF Compressor
Compress PDF files up to 90% smaller while maintaining readability. Reduce file size for easier email sharing & faster uploads. Free PDF compression.
Upload a PDF to optimize and reduce its size.
About PDF Compressor
Free Online Tool
PDF Compressor
Reduce PDF file size for email attachments, uploads, and storage — without destroying readability. Upload, select a compression level, and download a smaller file in seconds.
How to Use This Tool (30 Seconds)
- 1Upload Your PDF: Click the upload zone and select your PDF file.
- 2Choose a Compression Level: Select Low, Medium, or High compression. Low preserves near-original quality with modest size reduction. High achieves maximum size reduction with visible quality tradeoff on image-heavy pages.
- 3Preview File Size Estimate: The tool displays an estimated output file size before you compress — so you can switch compression levels and compare the size-quality tradeoff without downloading multiple versions.
- 4Download the Compressed PDF: Click 'Compress & Download.' The compressed PDF downloads with all text, links, and page structure fully intact — only image data is recompressed.
What PDF Compression Actually Does to Your File
A PDF file is a container holding multiple streams — text, fonts, vector graphics, and embedded images. Compression targets embedded image streams, which account for 60–90% of file size in most PDFs. The tool applies JPEG re-encoding to raster image objects at a reduced quality factor:
// PDF image stream compression quality factors
Low compression → JPEG quality: 85 (~15–30% size reduction)
Medium compression → JPEG quality: 60 (~40–60% size reduction)
High compression → JPEG quality: 35 (~65–80% size reduction)
// Text, fonts, and vectors are never recompressed
textStreams → flate (lossless ZIP) compression only
vectorPaths → untouched; no quality loss on line art
// DPI downsampling at High compression
if (imageDPI > 150) resample to 150 DPI for screen viewing
Text-only PDFs — contracts, reports, spreadsheet exports — compress very little because they contain minimal image data. A 2MB text PDF may only reduce to 1.8MB at High compression. Image-heavy PDFs — scanned documents, brochures, photo portfolios — compress dramatically, often achieving 70–80% size reduction at Medium quality without visible degradation on screen.
Compression Level Comparison
| Level | JPEG Quality | Typical Size Reduction | Best For | Print Safe |
|---|---|---|---|---|
| Low | 85 | 15–30% | Archiving, high-fidelity sharing | ✅ Yes |
| Medium | 60 | 40–60% | Email, web upload, general use | ⚠️ Screen only |
| High | 35 | 65–80% | Messaging apps, strict size limits | ❌ No |
⚡ Pro Tip
If Medium compression is not reducing your PDF enough, check whether the file contains embedded fonts with full character sets rather than subsetted fonts. Many PDF generators embed the entire font file — sometimes 200–400KB per typeface — even when only 30 characters from it are used. Font subsetting strips unused glyphs and retains only the characters present in the document. This alone can reduce a text-heavy PDF by 30–50% without touching any image data or affecting visual quality at all, making it a completely lossless size reduction that compression alone cannot achieve.
Frequently Asked Questions
Q: Will compressing a PDF damage the text or make it unreadable?
No. Text, fonts, hyperlinks, bookmarks, and vector graphics are never modified during compression. Only embedded raster image streams are recompressed. Text remains fully selectable, searchable, and crisp at all compression levels — only photos and scanned images are affected.
Q: Why is my PDF barely getting smaller after compression?
Your PDF is likely text-dominant with minimal embedded images. Text and vector content compresses very little because it is already stored efficiently using lossless flate encoding. For maximum size reduction on text PDFs, font subsetting and removing embedded metadata are more effective than image compression.
Q: Is the compressed PDF safe to use for legal or official documents?
Low compression is safe for legal documents — it applies minimal image quality reduction and preserves all document structure. Avoid Medium or High compression on documents containing scanned signatures, stamps, or official seals, as these are image objects and will visibly degrade at aggressive compression settings.
Q: Does compression affect PDF password protection or encryption?
Password-protected PDFs cannot be compressed without first removing the password. Encryption wraps the entire file structure, preventing the tool from accessing and recompressing internal image streams. Remove password protection before uploading, compress, then re-apply protection if needed.
Q: Can I compress a scanned PDF without losing the text content?
Scanned PDFs store pages as flat images — there is no selectable text layer, only a photograph of the page. Compression reduces the image quality of those scans. If the file has been OCR-processed and contains a text layer beneath the scan, that text layer is preserved. The visual scan image quality will reduce at higher compression settings.
Q: What is the maximum file size this compressor supports?
PDFs up to 50MB are supported. For very large files — high-resolution print PDFs, architectural drawings, or multi-hundred-page scanned documents — Adobe Acrobat's PDF Optimizer or Ghostscript offer batch compression with granular control over resolution and stream settings beyond what browser-based tools can handle.
Q: Will the compressed PDF look different when printed?
Low compression is print-safe — the quality difference is imperceptible in print. Medium compression is acceptable for standard office printing but may show artifacting on high-resolution photo prints. High compression is recommended for screen viewing only and will produce visible JPEG blocking on printed photos and gradients.