Most articles on this topic describe PDF compression the same way: "we shrink your images and subset your fonts." That's how some compressors work — but it's worth knowing exactly what happens to your specific file, because it changes what result you should expect.
Why PDFs Bloat in the First Place
- High-resolution images: the most common culprit by far. Ten 10 MB photos embedded in a document will produce a ~100 MB file even if the surrounding text is a single page.
- Scanned pages: each page is saved as a full image, often at 300 DPI or higher — dramatically larger than the same content as real text.
- Embedded fonts: PDFs often embed entire font files (every glyph, every weight) so the document displays identically everywhere, even if the document only uses a handful of characters from that font.
- Accumulated structure: a PDF that's been edited, re-saved, or exported repeatedly builds up redundant internal objects, incremental revision data, and duplicate resources that never get cleaned up.
What Our Compressor Actually Does — Honestly
ILoveConvert's Compress PDF tool does structural compression: it rebuilds the PDF's internal object table into compressed object streams and strips redundant structure. It does not re-encode, downsample, or re-compress the images inside your PDF, and it doesn't touch fonts.
That distinction matters more than it sounds:
- Text-heavy and vector-heavy PDFs (reports, invoices, exported slide decks, forms) often shrink noticeably — sometimes 20–40% — because a large share of their size was redundant object structure, and none of it is visual data, so there is genuinely zero quality loss. Not "no visible difference" — literally nothing about the rendered page changes.
- Image-heavy and scanned PDFs will shrink much less, because the bulk of the file is already-compressed image data (typically JPEG) sitting inside the PDF container. Repacking the container around already-compressed pixels doesn't meaningfully reduce that data.
If you upload a 50 MB scanned PDF expecting it to come out at 2 MB, structural compression alone won't get you there — and any tool telling you it will without touching your images is either doing something lossy it isn't disclosing, or overselling the result. We'd rather tell you upfront: for image-heavy files, the fix is re-exporting the source images at a lower resolution before you build the PDF, not compressing the finished PDF.
How to Compress a PDF on ILoveConvert
- Go to Compress PDF
- Upload your file
- Click Compress PDF — this runs in-browser upload, server-side processing, done in a couple of seconds for most documents
- Compare the before/after size shown on the result screen and download
If You Need a Scanned PDF Smaller
Since structural compression won't shrink embedded scan images, your realistic options are:
- Re-scan at a lower DPI. 150 DPI is legible for text documents and roughly a quarter the file size of a 300 DPI scan.
- Split it. If the document is large because it's long rather than because each page is heavy, splitting it into sections is often more useful than compressing — recipients can open what they need instantly.
- Share a link instead of a file. For scans you can't shrink further, a Google Drive or Dropbox link avoids the attachment-size ceiling entirely.
Attachment Limits Worth Knowing
- Gmail: 25 MB
- WhatsApp: 100 MB for documents
- Most business email servers: 10–25 MB
The short version: run it through the compressor first regardless of file type — it costs nothing and never makes a text-based PDF worse. Just don't expect it to work miracles on a stack of scanned receipts; for that, the fix happens before the PDF is created, not after.