Your design portfolio is 80 MB because every page has a hi-res image. Compressing it down means making decisions image by image — but you don't want to do that manually.
Image-heavy PDFs compress well, but the trade-off curve is sharper than text. Cross the line and the images look soft. Stay under it and no one notices.
Understand image compression in PDF
PDFs embed images at the resolution you exported them. A 300 DPI photo at A4 is around 2-4 MB. Most viewers display PDFs at 72-150 DPI. The extra resolution is wasted bytes.
Compression downsamples images to a target DPI. 150 DPI is the sweet spot for screen viewing; 300 for print quality.
Pick the right DPI target
If the PDF is going to be viewed on screen, 150 DPI is plenty. Drop to 150 in Flint's compressor and you'll cut file size by 60-80% with no visible loss.
If the PDF will be printed, 300 DPI is the floor. Compress more carefully — Medium setting only, and check the result on actual print.
Compress lossless where possible
Vector content (logos, diagrams) is compressed losslessly — no quality loss. Photos get lossy compression, which is where quality matters.
For portfolios and case studies, balance per page. Pages with vector content can be compressed harder. Pages with hero photos should stay closer to original quality.
Test at full screen
Compressed image quality is invisible at thumbnail size. It shows at full screen. Open the result, page through it, watch for softness, jagged edges, colour shifts.
If anything looks wrong, re-compress at a lower level. The first acceptable result is the one to ship.
FAQ
What DPI should I use for screen viewing?
150 DPI is the sweet spot. 96 DPI looks fine on most screens. 300 DPI is overkill unless the PDF will be printed.
Will compression destroy a portfolio?
Not if you compress thoughtfully. Medium setting preserves visible quality on portfolios. Don't compress portfolios on High — the difference is noticeable.
Can I compress some images more than others?
Most batch compressors apply one setting. For per-image control, re-export the source with the right resolution per image. More effort, more control.
Why is my photo PDF still big after compression?
Probably already saved at low DPI or with limited photos. Compression has less room to work. Consider splitting instead of compressing further.
Image-heavy PDFs reward careful compression. Drop yours into Flint's compressor, check at full screen, and ship the version that looks like the original.