Compress PDF

Drop out what a PDF does not need, and shrink its images if you want it smaller still. Your files are processed in memory and sent straight back; nothing is stored.

Signed and password-protected PDFs are left alone: rewriting them would break the signature or need the password.

In C#: PdfCompactor.Compact(pdf), or with new PdfCompactOptions { MaxImageDpi = 150, ImageQuality = 80 }. Compacting in the manual