GekiPDF

PDF JPEG Quality and Downsampling: What Changes When You Compress

Learn how JPEG quality and downsampling affect your compressed PDF. GekiPDF's compress tool uses Ghostscript presets from ~200 to ~96 DPI, no signup needed.

    Runs the same engine as our Compress PDF tool.

    When you compress a PDF, the biggest factor is what happens to the images inside. GekiPDF's compress-pdf tool rewrites your file using Ghostscript presets that downsample bitmaps to ~150 DPI by default (Recommended). That means each page's image is reduced in resolution, which cuts file size dramatically while keeping text readable. A 300 DPI colour page is about 1.2 MB; at 150 DPI greyscale, it's roughly 150 KB for the same page.

    The trade-off is visual detail. At Extreme preset (~96-120 DPI), fine lines or small fonts may look slightly softer if zoomed in, but on screen or print at normal sizes it's often unnoticeable. The Light preset keeps ~200 DPI for higher fidelity but yields larger files. Your text layer stays intact—only the bitmap data is altered. For a 16-page scan, compression takes about 1 second, and files are deleted after one hour.

    Frequently asked questions

    Does compressing a PDF reduce image quality permanently?

    Yes, it changes the embedded images by lowering their resolution (DPI) and recompressing them as JPEG. The original file isn't modified unless you replace it, so keep a backup if you need full quality.

    What is the difference between JPEG quality and downsampling?

    JPEG quality controls how much detail is kept per pixel (compression artifacts). Downsampling reduces the number of pixels per inch (DPI). Both affect file size; downsampling has a bigger impact on dimensions.

    Which preset should I choose for a scanned document with small text?

    Use Recommended (~150 DPI) as a balance. If text becomes blurry when zoomed, try Light (~200 DPI). Extreme (~96-120 DPI) works for photos but may make small characters hard to read.

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    Open Compress PDF for all options, or jump straight to another step below.

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