Fit several PDFs into one size-capped upload

Five documents, a 5 MB portal and a midnight deadline

Priya is submitting a research grant application. The funder's portal has one upload field, it accepts a single PDF, and the small print says "maximum 5 MB". Her pieces are a 14-page proposal exported from Word at 1.2 MB, a one-page budget table at 300 KB, a two-page CV at 250 KB, and two letters of support that her referees signed on paper and photographed with their phones, one at 8 MB and one at 6 MB. Together that is close to 16 MB, three times the cap, and the portal closes at midnight.

Her instinct is to shrink each file until the five numbers add up to less than 5 MB. That works badly. She would be guessing five targets, the proposal has almost nothing to give, and the letters would get squeezed again later if the total still came out too high. One join and one compression pass solve it with a single decision: which number to type.

Why joining comes before shrinking

Joining does not change the weight of a page. The merged file is roughly the sum of what went in, give or take a little structure, so nothing is lost by doing it first. Compression is the step that changes images, and it is happiest when it sees everything at once: it can spend its effort on the two heavy letters and leave the light text pages alone, without you deciding how to split a budget across five files.

Reversing the order also wastes quality. A letter shrunk on its own and then shrunk again as part of the bundle goes through image encoding twice, and each round softens photos a little more.

Two passes in PDFGym

1. Open Merge PDF and add all five files. Each appears with its page count and size.
2. Use the up and down arrows to set the order the reviewers expect: proposal, budget, CV, then the two letters.
3. Press the merge button. The result panel shows the total page count and the merged size next to the size of the originals. Download the file, which is named after the first document with "-merged" added.
4. Open Compress PDF and choose the merged file.
5. Type your target in the exact size field and pick MB or KB. For a portal that says 5 MB, type 4.7 MB (the next section explains why).
6. Press Compress. Several methods compete, and every candidate is read back and its text compared with the source before one is offered.
7. Read the verdict and look at the preview. If both satisfy you, download the file, which carries "-compressed" in its name, and upload that one.

Turning the portal's limit into the number you type

PDFGym counts a kilobyte as 1,024 bytes, so 200 KB means a ceiling of 204,800 bytes. Many upload forms count 1,000 bytes to the kilobyte instead, which makes their limit about 2.3% stricter in kilobytes and nearly 5% stricter in megabytes. Typing a slightly lower figure covers both ways of counting. The figures below are plain arithmetic.

Each suggested target sits under the strict reading, so the file passes whichever way the portal measures. If the limit is for an email rather than a form, aim lower still, because attachments grow by about a third in transit; the guide to sending two PDFs as one attachment works through that case.

Find the heavy part before you squeeze everything

In a bundle like Priya's, almost all the weight sits in a few pages, usually the photographed ones. PDF size breakdown shows which pages, images and fonts carry the bytes without changing the file, so you know whether compression can reach your number or whether something has to go.

If one letter is a 4,000-pixel phone photo of a single sheet, a cheaper fix may be to ask the referee for a scanned PDF instead. If a section is padding, such as a duplicated cover page or an appendix the funder did not request, removing it with Organize pages saves more than any setting.

Mistakes that cost you a second run

• Typing the limit itself as the target. A file of 4.99 MB by PDFGym's count can still be over a portal's 5 MB. Leave the margin from the table.
• Fixing page order after compressing. Rearranging the compressed file means rewriting it. Check the order in the merged file before the compression pass.
• Uploading the wrong copy. After two passes you hold three versions. Upload the one ending in "-compressed", and delete or archive the rest once the submission is confirmed.
• A locked source file. The merge tool refuses password-protected PDFs. Remove the password with the unlock tool first, using the password you already have.
• Ignoring the verdict when it misses. If the result stays above the target, it states by how much and offers one more pass that redraws page images smaller, with softer photos as the trade. Accept it, or cut pages instead.

When a single squeezed file is the wrong goal

Read the upload instructions twice. Many portals offer one field per document, and in that case each part only has to meet its own limit, which may need no compression at all. Fine detail can also be a reason to stop: a site plan or a chart with tiny labels may lose legibility when page images are pushed hard, and a reviewer who cannot read it is worse than a polite note asking whether a larger file is acceptable.

A PDF with a working digital signature should travel as its own file, because copying its pages into a new document does not keep the signature valid. And if the funder accepts links, a shared cloud folder avoids the cap altogether.