Optimize PDF
Clean up and optimize PDF structure by removing unused objects and rebuilding the file.
Optimize PDF Files Online - Free Tool
PDF optimization reduces file size and improves document compatibility by cleaning up the internal file structure and re-encoding images. This tool uses the same two-stage pipeline as the compress tool, with one key addition: the output is linearized, which restructures the PDF so the first page is available before the rest of the file finishes downloading. This makes linearized PDFs faster to open in browsers and web viewers. Your file is processed in server memory and deleted immediately after the result is returned. It is never written to disk.
What the Three Optimization Levels Do
Each level controls how aggressively images are downsampled and re-encoded. Text and fonts are not affected by any level.
| Low | Medium | High | |
|---|---|---|---|
| Image downsampling | None | 150 DPI bicubic | 96 DPI bicubic |
| Monochrome downsampling | None | 150 DPI | 120 DPI |
| JPEG quality | 80 | 70 | 52 |
| Best for | Print-ready files, portfolios | Reports, web publishing | Maximum size reduction |
After processing, the tool compares all candidate outputs and returns whichever is smallest. If a PDF is already well-optimized, the original may be returned unchanged.
When Optimization Works and When It Does Not
The amount of size reduction depends on what the PDF contains:
- Image-heavy PDFs see the largest reductions because image downsampling and JPEG re-encoding remove the most data.
- Scanned documents are stored as page images and compress well at Medium and High levels, though text sharpness decreases at 96 DPI.
- Text-only PDFs see little size reduction but still benefit from linearization, which improves load speed in web viewers.
- Already-optimized PDFs may see no size reduction. The tool will return the original in that case.
If your file is still too large after optimization, use the split tool to divide it into smaller sections. To extract and remove unnecessary images before reoptimizing, use the extract images tool.
How to Optimize a PDF
- Upload your file: Click the upload area or drag and drop your PDF. The file is sent to the server over an encrypted connection.
- Choose an optimization level: Select Low, Medium, or High depending on whether you need to preserve image quality or minimize file size.
- Remove metadata (optional): Check "Remove document metadata" to strip author, title, creator, producer, and other fields from the output file.
- Download the result: The server returns the smallest output it could produce. The file is deleted from server memory immediately after the response is sent.
FAQ
PDF optimization removes unused objects and redundant data from the file structure, re-encodes images at a lower quality based on the selected preset, and linearizes the output. Linearization restructures the PDF so the first page is stored at the beginning of the file, allowing web viewers and browsers to display it before the rest of the file finishes downloading. Text and fonts are not affected.
Both tools use the same image downsampling and re-encoding pipeline. The optimize tool additionally linearizes the output file, which improves load speed in browsers and web-based PDF viewers by making the first page available before the full file is downloaded. For offline use where load speed does not matter, either tool produces the same result. For PDFs published on websites or shared via web links, the optimize tool is the better choice.
Linearization is a way of organizing the internal structure of a PDF file so that the first page and its resources appear at the beginning of the file. A non-linearized PDF stores objects in arbitrary order, so a browser or web viewer must download the entire file before it can display any page. A linearized PDF allows the viewer to render the first page immediately while the rest of the file continues loading in the background. This is also called "fast web view" in some PDF tools.
If a PDF was already compressed before uploading, the tool cannot reduce it further through image re-encoding. Text-only PDFs also see minimal size reduction because there are no images to downsample. The tool compares all output candidates and returns the original if it is already the smallest. Trying a higher optimization level may produce a smaller result, at the cost of image quality. The file is still linearized regardless of whether the size decreases.
No. Text in a PDF is stored as vector outlines or font data, not pixels, so it is not affected by image downsampling. Only raster images are re-encoded. On scanned documents, where each page is a raster image, higher optimization levels reduce text sharpness because the text is part of the page image rather than stored as a separate vector layer.
Yes. The tool includes a Remove document metadata option that strips author, title, creator, producer, and other fields stored in the PDF info dictionary and XMP stream. Check the option before optimizing. The metadata is removed from the final output file after optimization completes.
No. The file is processed entirely in server RAM and deleted immediately after the optimized result is returned to your browser. It is never written to disk, stored in a database, or retained after the request completes.
Image-heavy PDFs such as presentations, brochures, and design exports see the largest size reductions. Scanned documents compress well because every page is a raster image. Text-only PDFs see minimal size reduction but benefit from linearization when published online. PDFs shared via web links or embedded on websites benefit from optimization regardless of size reduction, because linearization improves perceived load speed.
Yes. Scanned PDFs store each page as a raster image, which makes them good candidates for size reduction. The High level downsamples page images to 96 DPI and re-encodes them at JPEG quality 52. The tradeoff is reduced text sharpness because the text is part of the page image. If you need to extract text from a scanned PDF, use the OCR tool before optimizing.
Try the High level if you have not already. If the file is still too large, use the split tool to divide it into smaller parts. For documents with many embedded images, use the extract images tool to identify and remove unnecessary images before reoptimizing.