Compress PDF Files Online for Free

Compression modes by use case:

• ·Screen (72 dpi images) — Smallest files for email and online forms. Documents viewed only on screen look identical to the original. Not suitable for printing.
• ·Ebook (150 dpi images) — Good balance. Works for digital sharing, presentations, and contracts. Readable at 100% zoom on screen.
• ·Print (300 dpi images) — Preserves print quality. Reduces size only through font subsetting and metadata removal. Best for documents that will be professionally printed.
• ·Prepress (300 dpi, colour profiles preserved) — Minimal compression. For professional print workflows where colour accuracy matters.

Realistic size reduction by PDF type:

• ·Scanned documents (image-only PDFs): 60-80% reduction possible
• ·Mixed PDFs (text + images): 30-50% reduction
• ·Text-only PDFs: 10-20% reduction (mainly from font subsetting)
• ·Already-compressed PDFs: 5-10% or none

One rule: Compressing a PDF that was already compressed may not reduce size further. If you compressed it before, start from the original source file.

PDF vs DOCX for sharing: PDF is the right choice for documents you do not want recipients to edit. DOCX is smaller but editable. For contracts, invoices, and reports — use PDF.

PDF compression vs PDF conversion: Compression keeps your document as a PDF. Conversion (PDF to Word, PDF to image) changes the format entirely and is a separate operation. Compress when you need to keep it a PDF; convert when you need an editable or image-based version.

Lossless vs lossy PDF compression: Lossless compression (font subsetting, metadata removal, stream re-encoding) is always safe. Lossy compression (image quality reduction) is what gives the largest size reduction but permanently discards image data. Both are applied here — you control the image quality threshold.

PDF file size is determined by three things: embedded images, embedded fonts, and content streams. Understanding which of these is making your PDF large is the first step to compressing it effectively.

Embedded images are usually the largest contributor — especially in PDFs created from scans, screenshots, or high-resolution photos. These can often be recompressed at slightly lower quality with no visible difference. Embedded fonts are the second contributor: many PDFs embed entire font families even when only a handful of characters are used. Font subsetting — keeping only the characters that actually appear — can cut font data by 80%. Content streams (the PDF drawing commands) are usually already compressed and contribute the least.

This compressor handles all three layers: recompresses embedded images at a quality level you control, subsets embedded fonts, strips metadata (creation software info, thumbnail previews, author data) that adds size without adding value, and flattens transparency where possible. Your file never leaves your browser.