How to reduce PDF size without losing what matters
Choose between structural optimization and image-based compression.
VertexFiles editorial · Updated 6 September 2026
First, identify the kind of document
A PDF made from a word processor usually contains text, fonts and perhaps a few images. A scanned document often contains a large photograph on every page. These files respond differently to compression. Open the original, zoom in, and try selecting a sentence. If selection works, there is probably a text layer worth preserving.
Try structural optimization first
Structural mode rewrites the document with compact object streams. It leaves page text and images intact, so the result may be only slightly smaller. An already optimized PDF can even grow. Compare the reported byte sizes and keep the original when there is no benefit. This mode is not a promise of a particular percentage reduction.
Use image mode only when its trade-offs fit
Image mode renders each page and builds a fresh PDF from JPEG images. Lower resolution reduces dimensions; lower quality reduces image detail. Start around 120 DPI for ordinary on-screen reading and inspect small print. The rebuilt file loses selectable text, links and interactive forms. Never use that copy as the only editable archive.
Check the actual download
Open the output and inspect the first page, a page with the smallest text, and the last page. Confirm the page count, orientation and legibility. If an upload portal requires a maximum size, compare the exact output size rather than assuming a compression setting guarantees acceptance.