优化图片

It locates the embedded images inside your PDF, downscales ones that are larger than needed, and recompresses them with efficient settings. Because images are usually the bulkiest part of a document, this typically produces a much smaller file while keeping pages looking sharp.

Yes. You can set a JPEG compression quality level and a maximum resolution for the longest side of each image. Lower settings shrink the file more aggressively, while higher settings preserve more detail, letting you balance size against visual sharpness.

No. The tool detects images with transparency and re-encodes them as PNG to preserve the alpha channel, while opaque photos are compressed as JPEG for maximum savings. Transparent logos and overlays keep their see-through areas intact rather than gaining a solid background.

Some specialized formats, such as certain CMYK, JBIG2, or JPEG2000 streams, can't be re-encoded in the browser. The tool simply skips those images and continues optimizing the rest, so the job completes successfully instead of failing on an unsupported picture.

Yes. All downscaling and compression runs locally on your device, and nothing is uploaded to a server. Your PDF stays private, which is ideal for shrinking confidential reports or presentations before emailing them, all completely free of charge.