Optimize PDF file size
Try lossless structure optimization and compare the result.
What Optimize PDF file size helps you do
Resave a PDF using object streams to reduce some structural overhead. This can help PDFs with uncompressed document objects, but scanned or already optimized files may stay the same size or become larger.
How to use it
- Select one unencrypted PDF.
- Run optimization. Image resolution and image quality are not reduced.
- Compare original and output sizes, and keep the original if the result is larger.
Input and output example
A PDF with many uncompressed document objectsOUTPUT
A PDF resaved with object streams; savings depend on the source
Supported formats and limits
- One PDF at a time. Page-order and stamping edits are not part of this operation.
- Unencrypted PDFs only. Up to 10 files, 25MB per file, 50MB total and 200 pages. Files are processed in your browser; damaged or unsupported PDFs are rejected.
- Page-copy operations may omit document-level bookmarks, attachments and interactive form behavior. Editing may invalidate digital signatures. Keep your original and check the downloaded PDF.
- Word/Excel conversion and searchable-PDF OCR are not included. For English image OCR, export a PDF page with PDF to JPG and PNG, then use Image to Text.
How the result is calculated
pdf-lib rewrites the PDF with object streams. This is structural optimization, not image recompression, downsampling or OCR. No specific size reduction is promised.
Frequently asked questions
Why is my optimized PDF larger?
The source may already be efficiently compressed, or the new document structure may have more overhead. When no reduction is achieved, the tool says so and recommends keeping the original.
Can this make a scanned PDF much smaller?
Usually not, because it does not recompress embedded images. You can compress the original pictures and rebuild a PDF, or use a dedicated offline PDF program for image downsampling.