A PDF gets large for one of three reasons: photos at very high resolution, scanned pages saved as pictures, or embedded fonts and graphics. Compression works best when it targets the first two, because text and vector drawings take up little space to begin with.
Step 1: Check what is making the file big
If the pages are mostly text, the file is probably large because of images or scans. If the file is one image per page, the scan settings are the problem. Knowing this tells you how much you can shrink it.
Step 2: Set a target size
Pick the number your portal or email server needs. Common limits are 1 MB, 500 KB and 200 KB. Open Compress PDF and type the size, or tap a preset.
Step 3: Run it and check the result
The tool lowers image resolution and quality in steps, and stops as soon as the file is under your target. It reports the size it reached. If the target is not reachable, the smallest version is returned along with the reason.
Tips for better results
- Compress the original file, not a copy that was already compressed. Each pass loses a little more detail.
- Keep the text as selectable text. Converting pages to images to save space makes text unsearchable.
- Check photos and logos after compressing. Very small targets blur fine detail.