Guide
How to compress a PDF in C#
Call Compress(dpi, quality) on the loaded document, then save the result.
This recompresses eligible streams in the PDF. The main setting you will usually care about is the JPEG quality value.
The shortest working example
Load the PDF, call Compress(...), then save.
using ZingPDF;
using var pdf = Pdf.Load(File.OpenRead("input.pdf"));
using var output = File.Create("compressed.pdf");
pdf.Compress(dpi: 144, quality: 75);
await pdf.SaveAsync(output);Arguments
The method takes two values:
dpi: reserved for future image downsampling behavior and must be greater than zeroquality: JPEG recompression quality from 1 to 100
In practice, the quality setting is the one that matters most today.
What compression does here
Compression works on eligible streams in the document and can recompress JPEG image streams.
If your file is image-heavy, this is the high-level path to try before moving into lower-level PDF stream work.
Need to watermark before the final save?
Compression often sits near watermarking or metadata updates in the same output path.