Compress PDF — Reduce File Size Up to 70% Free
Smart PDF Compression
Select or drop PDFs to compress
Batch supported · Preserves all links, forms & annotations
Up to 70% Smaller
Reduce file size dramatically while maintaining quality using advanced compression algorithms.
Quality Preserved
Smart compression maintains readability and visual quality. Preserves all links, forms, and annotations.
100% Private
Your PDFs never leave your device. All compression happens locally in your browser.
Reduce your PDF file size by up to 70% while maintaining excellent quality using our advanced PDF compression tool. The compressor optimizes images, fonts, and metadata to make your PDFs smaller and faster to share. 100% private — compression happens entirely in your browser with no upload required. No file size limits, no watermarks, completely free.
How to Compress a PDF — Step by Step
Upload your PDF: Click the upload area or drag and drop. Large presentations, scanned documents, and image-heavy reports are supported.
Choose compression level: Light (20–30%) preserves professional image quality. Medium (40–50%) is perfect for email, sharing, and CVs. Heavy (60–70%) gives maximum size reduction.
Compress and download: Click "Compress PDF Now". Most files finish in 5–30 seconds. Download instantly — no watermark ever added.
Review results: Compare original vs compressed size. If quality looks fine, you're done. If you need it smaller still, try Heavy compression or split the PDF first.
Compression Level Guide
Professional Print
300 DPI images. Output is indistinguishable from the original. Best for portfolios, design work, and documents you'll print.
Best for: Portfolios, print-ready documents
General Use
150 DPI images. The sweet spot for CVs, reports, contracts, and email attachments. Looks identical on screen.
Best for: Email, CV sharing, office use
Maximum Compression
72 DPI images. Smallest possible file size. Text stays perfectly sharp; photos may look slightly softer.
Best for: Archiving, upload portals, 1MB targets
Why Compress PDFs?
📧 Email size limits
Gmail caps attachments at 25MB. Outlook at 20MB. Medium compression handles most PDFs in seconds.
📋 Upload portals & job applications
Government portals, HR systems, and university forms often impose 2–5MB limits. Heavy compression gets you there.
☁️ Cloud storage savings
Cut storage costs 50–70%. Compress archived PDFs in bulk to reclaim gigabytes.
📱 Faster mobile sharing
Smaller files open instantly on WhatsApp, Telegram, and email on any mobile connection.
🔒 Privacy-first
PDFNinja never uploads your file. Zero server contact. Works offline.
📊 Scanned document archives
Turn 15MB scanned documents into 2–3MB files without losing any readable content.
How PDF Compression Works
PDFNinja applies several simultaneous optimizations to shrink your PDF:
Image downsampling: Photos and raster graphics are resampled from high DPI to optimal screen/print resolution using bicubic interpolation — the highest-quality downsampling algorithm.
JPEG recompression: Images are re-encoded at a quality level matched to your chosen compression tier. Light = 92% quality. Medium = 75%. Heavy = 50%.
Page rasterization: For Medium and Heavy, each page is rasterized in your browser and re-embedded as a single compressed JPEG — this is where the bulk of the size savings come from.
Object stream packing: The output PDF is written with cross-reference object streams enabled, which is a smaller, more compact PDF encoding than the classic format.
Fully local: Everything runs in your browser using pdf-lib and pdf.js. Your PDF is never uploaded to a server at any stage of compression.
Frequently Asked Questions
Will compression make my PDF text blurry?+
Never. Text in PDFs is stored as vector data — it is never converted to pixels during compression. Text stays perfectly sharp and fully selectable at every compression level.
How do I compress a PDF to under 1MB?+
Choose Heavy compression. If still over 1MB, the PDF has many high-resolution images. Split it into sections first, then compress each section.
How do I compress a PDF for email?+
Most email clients allow up to 25MB. Medium compression handles most PDFs. Switch to Heavy if still over the limit.
Does this work without uploading my file?+
Yes. Everything runs locally in your browser using WebAssembly. Your PDF never reaches any server. It also works fully offline.
Can I compress a password-protected PDF?+
Remove the password first (use the Remove Password tool), compress, then re-encrypt if needed.
Is there a file size limit?+
No artificial limit. Practical constraint is your device RAM — usually 100–150MB on desktop.