Quick answer
University application portals often have strict file size limits, sometimes as low as 500KB or 1MB for important documents like transcripts, certificates, and letters of recommendation. When you're trying to meet a deadline, seeing a 'file too large' error can be incredibly stressful.
The reason universities use these limits is to manage the storage and processing of thousands of applications. However, high-quality scans of multi-page documents often result in files that are far too large for these systems.
What usually works best
For transcripts and multi-page certificates, PDF is almost always the required format. The challenge is reducing the file size without making the small text or official seals unreadable. This is where targeted PDF compression becomes essential.
If you're uploading a single-page certificate as an image, JPG is usually your best bet. It offers a great balance between file size and readability. Aim for a target slightly below the portal's limit—for example, if the limit is 1MB, target 1024KB or even 900KB to be safe.
If it still fails
For multi-page PDF documents, start with a 1MB target. If the portal is even stricter, like 500KB, use the 'smaller-file' profile and check the readability of the resulting file. It's vital that admissions officers can still see your grades and the institution's official marks clearly.
A useful workflow for students is: scan your documents at a reasonable resolution, combine pages into a single PDF if necessary, and then use ExactSizer to hit the portal limit in one pass. This avoids repeated attempts with generic compressors while keeping the document readable.