Compress PDF files online for free with ImageWizo. Reduce PDF file size using the available options, compare the result, and download your compressed PDF.
ImageWizo PDF Compress is an intelligent in-browser document optimization and byte-reduction utility engineered to shrink bloated PDF documents while strictly preserving typography clarity, vector line work, and document structure. By re-encoding embedded raster image XObjects, applying optimized DCT quantization filters, and removing redundant stream overhead within local browser memory, this tool enables users to shrink multi-megabyte scanned files down to lightweight documents that satisfy strict email attachment caps (e.g. 5 MB or 10 MB) and governmental submission limits. Executed entirely inside client device RAM using pdf-lib and PDF.js with zero remote server upload queues, your sensitive contracts, tax records, and legal briefs remain strictly confidential.
Local File Processing: File processing is performed locally in your browser rather than uploaded to an ImageWizo processing server. All processing for PDF Compress happens directly inside your web browser using client-side technologies and local device memory.
When you upload a PDF, the browser reads the file into a local ArrayBuffer and parses the document catalog. The compression engine analyzes internal PDF dictionaries to locate embedded raster image XObjects, which typically account for over 85% to 95% of a PDF’s total byte weight. Using off-screen canvas contexts, the engine downsamples oversized image matrices (e.g. downsampling 600 DPI raw scanner streams to 150 DPI screen-optimized densities) and re-encodes color streams using balanced DCT JPEG compression. Redundant font subsets and orphaned cross-reference table entries are purged, and the optimized document structure is reconstructed using pdf-lib. Supported file processing is performed locally in the browser rather than on an ImageWizo processing server.
Drag and drop any PDF file into the upload zone or select it via your local file browser.
Select from Low Compression (Maximum Quality / 85% fidelity), Medium (Balanced / Recommended), High Compression (Smallest File / 50%), or Custom settings.
Click Compress PDF to execute high-speed client-side image stream re-encoding and dictionary minification in local memory.
Review the live metrics card displaying original size, compressed size, saved bytes, and exact percentage reduction.
Download your lightweight, optimized PDF document immediately with a single click.
Pre-calibrated presets for Low (High Quality), Medium (Recommended Balanced), and High Compression (Maximum Byte Reduction).
Keeps font vectors, digital forms, and embedded hyperlinks razor-sharp while optimizing embedded raster image streams.
Instantly displays exact original file size, compressed file size, saved kilobytes, and percentage reduction.
Compress multiple PDF files concurrently in local device memory and bundle results into a clean ZIP archive.
Your confidential documents are processed locally on your device rather than uploaded to an ImageWizo processing server.
Completely free with no account creation, no daily caps, and zero watermarks added to your documents.
Compress 25 MB scanned passport, visa, and birth certificate documents down to under 2 MB to pass portal validation.
Compress voluminous court filings and multi-year accounting ledgers so they can be sent as standard email attachments.
Shrink multi-page resume and portfolio PDFs down to under 1 MB to pass university and employer upload constraints.
Compress high-resolution diagnostic scans and clinical charts for fast electronic health record (EHR) transmission.
PDFs created by office scanners contain raster images and experience dramatic 70% to 90% size reductions. PDFs composed purely of typed vector text and system fonts have very little raster overhead to compress.
Medium compression is the universal sweet spot for documents containing text and photos. High compression should be reserved for strict upload limits (e.g., under 1 MB) where slight image softening is acceptable.
The engine prioritizes text legibility, ensuring small footnote typography and signature lines remain completely readable even under high compression.
Encrypted PDFs cannot have their stream dictionaries analyzed or re-encoded without prior password decryption.
Solution: If a PDF contains no embedded images and only typed text, it is already extremely lean. Compressing will yield minimal byte savings.
Solution: High compression applies aggressive image downsampling. For fine art and photography portfolios, choose Low Compression (Maximum Quality).
Solution: Remove the open password in your desktop PDF viewer before loading the file into the compression engine.
Solution: Re-compressing already quantized image streams introduces generational artifacts with negligible additional byte savings.
Possible Cause: The PDF is comprised almost entirely of vector text, system fonts, and vector paths with zero raster image streams.
How to Fix: The document is already at near-optimal efficiency; no further raster compression is possible.
Possible Cause: The compression preset was set to "High Compression", which applies aggressive downsampling.
How to Fix: Re-compress the document using the "Low" or "Medium" preset to maintain higher image sharpness.
Possible Cause: The uploaded PDF is protected with an owner or user security password.
How to Fix: Unlock the password security restriction using your native PDF software before compressing.
Possible Cause: Re-encoding hundreds of high-resolution image streams simultaneously requires significant CPU and memory.
How to Fix: Compress the document on a desktop computer with ample RAM, or split into smaller sections first.
The Medium preset typically shrinks scanned documents by 65% to 80% while keeping photos crisp and text razor-sharp.
Review the computed byte metrics card to confirm that the new file size satisfies your target email or portal limit.
After merging multiple heavy documents together, run the consolidated file through PDF Compress to keep your bundle lightweight.
Always keep your uncompressed high-resolution original scan files in your local archives for permanent record-keeping.
Yes. ImageWizo PDF Compress is 100% free with no registration, no daily conversion limits, and zero promotional watermarks added to your documents.
File size reduction depends on document content. Scanned documents and PDFs containing high-resolution images typically shrink by 60% to 85%. Pure vector text documents experience smaller reductions because text is already compact.
No. The compression engine specifically targets and optimizes embedded raster image streams while preserving native vector typography, fonts, and text curves with razor-sharp clarity.
No. Supported PDF processing is performed locally inside your device browser memory using pdf-lib and client-side canvas routines rather than being uploaded to an ImageWizo processing server. Your confidential paperwork remains strictly private.
ImageWizo provides Low Compression (High Quality / 85% fidelity), Medium (Balanced / Recommended), and High Compression (Smallest File / 50% fidelity).
Yes. ImageWizo automatically calculates and displays the original file size, compressed file size, saved kilobytes, and the exact percentage reduction in real time.
No. For security and cryptographic integrity, password-protected PDF documents must be unlocked before their internal streams can be analyzed and compressed.