PDF Compress

The PDF Compress tool reduces PDF file size for email sharing, web publishing, and storage efficiency. PDFs with many embedded images are often unnecessarily large; compression reduces them to manageable sizes while keeping text and essential content readable. Typical reductions: 50-80% for image-heavy PDFs, 10-30% for text-heavy PDFs.

Choose a compression level: light (small reduction, high quality — good for professional documents), medium (balanced, typical for email sharing), or strong (maximum reduction, some quality loss — good for quick sharing of draft documents). Image resampling reduces embedded image resolution to what\u2019s necessary for screen or print. Font optimization removes embedded font data that isn\u2019t needed. All processing runs in your browser using PDF manipulation libraries, so documents stay local.

PDF size reduction comes from several techniques:

1. Image recompression:
- JPEG images: re-encode at lower quality
- PNG images: convert to JPEG if photographic (lossy but smaller)
- Raw images: compress with JPEG or JBIG2

2. Image downsampling:
- 300 DPI images downsampled to 150 DPI for screen viewing (cuts size 4x)
- 600 DPI scans downsampled to 300 DPI for standard printing

3. Font subsetting:
- Embedded fonts often include all glyphs; subset to only used characters
- Significant savings on documents that use only basic Latin subset

4. Removing duplicate resources:
- Same image embedded multiple times can share one reference
- Color profiles, fonts, forms can deduplicate

5. Removing metadata:
- Creator info, edit history, unused objects
- Annotations and comments if not needed

6. Stream compression:
- Content streams compressed with Flate (zlib) or other algorithms

Compression levels (typical):
- Light (Quality 80, 200 DPI): 10-25% reduction, minimal visible change
- Medium (Quality 60, 150 DPI): 30-50% reduction, slight image softness
- Strong (Quality 40, 100 DPI): 50-80% reduction, noticeable compression artifacts

Text-heavy PDFs: minimal savings because text itself is already compressed. Most reduction comes from embedded fonts and images.

Image-heavy PDFs: significant savings possible. A 50 MB scanned document with 300 DPI images can shrink to 10-20 MB at 150 DPI with acceptable readability.

Print vs screen: if the PDF will be printed, keep 300 DPI. For screen-only viewing, 150 DPI is plenty; 96 DPI is OK for casual reading.

Color vs grayscale: converting color images to grayscale or B&W (if color isn\u2019t essential) reduces size further.

PDF optimization libraries (in browser): pdf-lib, muPDF.js. These libraries parse PDF structure and apply optimizations.

Original PDF compression: PDFs often compressed at creation. Re-compressing doesn\u2019t help much and may degrade quality. If the PDF is already optimized, further compression produces little reduction.

Password-protected PDFs: need password to compress. Output is unprotected unless re-encrypted.

Performance: compression is computationally intensive. Multi-hundred-page PDFs may take 30 seconds to several minutes depending on image content.

Compared to Adobe Acrobat Pro Reduce File Size, this tool is free and browser-based. Acrobat offers more granular control over compression types; this tool uses sensible presets.

Compared to Ghostscript (gs) on command line, this tool has a browser UI. Ghostscript is more powerful for scripted batch compression; this tool is interactive.

Compared to online compressors, this tool doesn\u2019t upload your PDF. Many online services upload to their servers; this tool runs entirely in your browser.