PDF Compressor

Reloads a PDF with pdf-lib and re-saves it using object streams, a more compact way of storing the PDF's internal objects — this can shrink file size for documents with many objects, such as lots of pages, form fields, or fonts, but does not recompress or downsample embedded images.

Upload a PDF. It's processed automatically; when done, you'll see the original and optimized file sizes and a download button for the result.

useObjectStreams: true tells pdf-lib to group compressible PDF objects, like the cross-reference table and low-level object definitions, into compressed object streams instead of writing each one separately — a structural, lossless optimization defined in the PDF specification (ISO 32000), not an image or content change.

A text-heavy PDF with many pages, fonts or form fields, previously saved without object streams, can shrink meaningfully. A PDF whose size is dominated by embedded photos or scans changes very little, because this tool doesn't touch image data — the images were likely already compressed (JPEG) by whatever created the PDF, and pdf-lib doesn't re-encode or downsample them.

This does not recompress, downsample, or reduce the resolution of embedded images — the single largest lever for shrinking most real-world scanned or photo-heavy PDFs. It doesn't remove unused objects, flatten form fields, or strip metadata, and it requires the file to load successfully in pdf-lib; encrypted PDFs are opened with encryption ignored, which can produce unexpected results for password-protected files.

Object streams are part of the PDF 1.5+ specification (ISO 32000), supported by virtually all modern PDF readers. Processing runs entirely in your browser using the pdf-lib library; your document is never uploaded to a server.