A PDF can be heavy for very different reasons. A certificate scanned by a phone app is a few megabytes because each page is really one large photograph; a report exported from Word is heavy because the exporter saved every font and image loosely. This page does not ask you to know which case you have. You type the size the form allows, and the compressor works through its stages until the file fits.
The limit is a hard one, checked on the finished file, with 1KB counted as 1,024 bytes. Anything from a single page to a few hundred pages can go in. If the result needs to stay above a lower figure as well, the minimum switch pads the file into the range, and if the PDF already fits, the page tells you so and leaves it alone.
How to use it
- Drop a PDF on the box above or tap it to pick one from your files.
- Enter the maximum size and choose KB or MB. Portals usually quote the figure in the field label or on the instructions page.
- Press Compress. The result card names the stage that was needed, the page count and the size before and after.
- Download the new file, or type a different limit and run it again if you want a lighter or a sharper copy.
Three stages, stopping at the first that fits
The first stage changes nothing you can see. The file is rewritten in a tighter structure: objects that nothing refers to are dropped and the internal tables are packed. Files exported loosely from office programs often lose a good part of their weight here, and the text remains selectable. If that is not enough, the second stage goes after the photos and scans embedded in the pages. Their JPEG quality is lowered step by step, each result measured, and when quality alone falls short they are scaled down as well. Text, lines, vector drawings and form fields are left exactly as they were.
Only when the file is still too large does the third stage run. Every page is rendered as a picture and a new PDF is built from those pictures at the quality and resolution that fit the limit. The pages keep their size in centimetres, so a printout looks the same, but the words are now part of an image: they cannot be selected, copied or searched, and a very tight limit on a long document makes them soft. The result card says which stage was used, so you know what you are handing in.
Scans and text documents behave differently
A scanned document is usually one big photograph per page with nothing else in it, so the second stage is what shrinks it. A 300 DPI colour scan of an A4 page is 1MB to 3MB as a JPEG, while a 150 DPI greyscale scan of the same page is about 150KB to 400KB, which is why greyscale originals reach small limits with far less visible loss. A document typed in Word or exported from a billing system has real text and often fits after the first or second stage, with every line still selectable.
Minimum sizes, locked files and long documents
Some document fields reject files that are too light as well as too heavy. Tick the box marked “My form also has a minimum size”, enter the lower figure, and unused padding data is added inside the file structure whenever the result would otherwise land below it; the pages are not touched and no viewer shows the padding. A PDF that needs a password to open cannot be processed and the page says so, while a file that only restricts printing or copying goes through without those restrictions. A few hundred pages are fine for the first two stages; the third is limited to about 150 pages on a phone.
Frequently asked questions
- What do “structure only”, “photos re-compressed” and “pages saved as pictures” mean?
- They name the stage that reached your limit. Structure only means the file was repacked and nothing visible changed. Photos re-compressed, text kept means the embedded images were lowered in quality or size while the text stayed selectable. Pages saved as pictures means every page was rendered as an image, so the text can no longer be selected or searched.
- Does the tool stop when the file is already small enough?
- Yes. If the PDF is already at or below the limit you typed, the page says so and offers the original unchanged. Compressing it further would only cost quality for no gain, so nothing is re-encoded.
- How is a KB measured here?
- As 1,024 bytes, with 1MB equal to 1,024KB, the convention Windows and most portals follow when they report a file size. A 500KB limit therefore allows 512,000 bytes. If a portal appears to count in round thousands, type a slightly lower figure and the file passes under either reading.
- Can it handle a 200-page PDF?
- For the first two stages, yes; a few hundred pages are fine. The third stage, which rebuilds pages as pictures, is limited to about 150 pages on a phone because of memory. For a long scan with a tight limit, split it first or run the job on a computer.