Disclaimer
What PDF compression can—and cannot—do.
Results vary
Reduction depends on embedded images, existing compression, fonts and document structure. An already optimized PDF may not become smaller. The tool reports actual byte sizes rather than estimated savings.
Image quality
Recommended and Strong modes may resize and re-encode compatible JPEG images. High Quality uses gentler JPEG settings. All image re-encoding is potentially lossy; none of these modes is advertised as lossless.
Supported content
Only compatible standalone 8-bit RGB JPEG images are re-encoded. Images with masks, special color spaces or custom decode parameters are left unchanged. Other image formats may receive no image-size reduction. Text and vector page content are not rasterized.
Document integrity
Encrypted and signed documents are rejected. Complex forms, archival conformance and unusual PDF features may not survive rewriting exactly as expected. Always inspect the result and retain the original. Large or complex PDFs may exceed a mobile device’s available memory.