Where a 300 KB limit shows up
A 300 KB cap is tight. You tend to meet it on older upload systems and on forms that collect many small attachments at once: a supporting document for a benefits claim, a proof of address for a utility account, a certificate attached to a membership or licensing renewal, or a single-page form in an online application that also asks for a photo and a signature.
These limits are usually there to keep a server or a database small, not because the person reviewing your file needs it that light. That's good news: a one-page or two-page document can usually fit while staying readable, as long as you compress it with a clear target in mind instead of guessing.
How ConvertirDocs reaches 300 KB
Type a target and the engine works on the photos inside the PDF, which is where almost all the weight lives in scanned documents. It lowers their quality and resolution in steps and stops as soon as the file is under 300 KB, so you don't lose more detail than the limit demands.
Text and vector graphics are never recompressed. If your PDF was created digitally, its words stay sharp and selectable however small the file gets. Embedded page thumbnails and XMP metadata are removed too, since nobody sees them. When the target is met, you'll see the size before, the size after and the percentage saved.
Make the job easier before you compress
Three hundred kilobytes leaves little room for extra pages. If the form only needs the first page of a long document, keep just that page with “Extract pages” and compress the result. Remove blank backs of scanned sheets with “Remove pages”. Every page you drop is weight you don't have to squeeze out of the rest.
If you're scanning from paper, the scan itself matters. A grayscale or black-and-white document filter weighs much less than full color, and cropping off the table or desk around the sheet removes wasted pixels. “Scan to PDF” does both with your phone's camera, and you can send its result straight to the compressor without selecting the file again.
When 300 KB isn't possible
Some PDFs can't get that small. A long document with dozens of scanned pages, a file whose weight comes from embedded fonts, or one built from image types the engine leaves intact (transparent, 1-bit, indexed, CMYK, JPX or JBIG2) may stay above the target. In that case you get the smallest file achieved and a short explanation, never a silent failure.
Your options then are to send fewer pages, split the document with “Split PDF” if the portal accepts several files, or ask whether a larger limit applies to multi-page documents. Everything runs in your browser: the file isn't uploaded, and ConvertirDocs adds no watermark to your document.