What Compress PDF does
Compress PDF offers two distinct browser-side methods. Raster image compression renders every page as a JPEG and rebuilds the PDF, which can substantially reduce image-heavy scans. Structural optimization reloads and rewrites the PDF without intentionally rasterizing pages, which can remove some structural overhead but may make little difference to an already optimized file.
The result panel compares original and output sizes instead of assuming success. Compression is content-dependent: a scan with large images may shrink, while a concise vector document can become the same size or larger. Keep the source unless the reviewed output meets both visual and functional requirements.
When to use this tool
Use compression when a document exceeds an email, portal, or storage limit and source-application export settings are not available. Raster mode is most suitable for scan-like pages where a visual copy is acceptable. Structural mode is the cautious first attempt for documents that should retain text and vector content.
If a source application can export a smaller PDF directly, that route often preserves more structure. Removing unnecessary pages or oversized source images before PDF creation can also be more effective than post-processing.
- Reduce a scanned packet before uploading to a size-limited portal.
- Try a lossless rewrite on a PDF with avoidable structural overhead.
- Create a lighter visual review copy of an image-heavy report.
- Compare quality levels before choosing a distribution version.
How to compress a PDF
- Keep the source file and select it in the compression tool.
- Choose Structural optimization first when searchable text and links matter.
- For stronger raster compression, choose JPEG quality and render resolution.
- Select Compress PDF and wait while each page is processed.
- Compare sizes, download the result, and inspect text, images, links, forms, and printing.
Practical examples
A 30 MB scan must fit under a 10 MB portal limit. Raster mode with balanced quality and standard resolution may reduce it significantly because every page is already image-based. Inspect small print and signatures. If detail is inadequate, increase quality or resolution and accept a larger file.
A 900 KB digitally generated contract contains selectable text and links. Structural mode is the appropriate first test. If the result becomes 940 KB, the tool correctly reports that it is larger. Keep the original rather than using a worse output simply because it has “compressed” in its filename.
Tips for better results
- Try structural optimization before rasterizing a text-based document.
- Test representative pages at balanced settings before processing a long scan.
- Lower JPEG quality gradually; avoid sacrificing legibility for a small size gain.
- Remove unnecessary pages before compression to reduce work and output size.
- Measure against the real upload limit and retain the smallest acceptable reviewed version.
Planning and quality checks
Define acceptance criteria before changing settings: maximum bytes, minimum readable text size, required searchable text, color expectations, and features that must still work. A smaller output is not a success when it fails the receiving portal's page rules, loses necessary links, or makes signatures difficult to inspect. Record the chosen method so recipients understand whether they received a structural rewrite or flattened visual copy.
Compare representative content at high zoom and normal viewing size. Inspect fine text, photographs, line drawings, gradients, stamps, and pages with unusual dimensions. Then test search, copy, links, forms, printing, and accessibility when those functions matter. Raster mode should normally be described and named as a flattened review copy. Keep the original as the authoritative version unless the document owner has explicitly approved the compressed derivative for its intended use.
Limitations and important details
Raster mode converts pages to images. It removes searchable text, vector precision, links, form behavior, accessibility tags, and other interactive structure, and it can invalidate signatures. It can also increase file size for simple pages. Structural mode does not recompress every embedded asset and is therefore not a guaranteed optimizer.
Large, high-resolution, or long files can exceed available browser memory. The tool does not offer OCR, monochrome scan encoding, font subsetting controls, object-by-object analysis, PDF/A validation, or guaranteed target-size output. Professional publishing and archival workflows need specialized software.
Frequently asked questions
Which compression method should I choose?
Use Structural optimization when preserving text and vectors matters. Use Raster image compression for stronger reduction of scan-like documents when a flattened visual copy is acceptable.
Can the output be larger?
Yes. The tool reports the actual size difference. Already optimized or simple files may not benefit from rewriting.
Will raster compression keep searchable text?
No. It renders each page as a JPEG image and does not run OCR.
Can I specify an exact output size?
No. PDF content varies too much for this browser tool to guarantee a target size.
Does structural optimization preserve everything?
It avoids deliberate rasterization, but any PDF rewrite can affect advanced features and signatures. Review the output carefully.