Merge Scanned Documents into One PDF Under 200 KB for an Application Portal

A typical requirement

The West Bengal scholarship portal's NMMSE 2026 instructions are a good example of the rules you'll meet. Certificates such as income and caste certificates are uploaded as scanned PDF documents, and the maximum size of each scanned PDF is 200 KB. The photo is separate, a JPG of up to 50 KB. Other portals phrase it differently, sometimes with a minimum as well, so read your own notice for the exact numbers and which documents go into which slot.

When one slot must hold several pieces of paper (a two-sided mark sheet, an ID card front and back, a covering letter), you have to merge before you upload, and merging is where file sizes get out of hand.

Why merged scans are so big

Merging and converting don't compress anything. When you turn JPG photos into a PDF, the image-to-PDF tool places each JPEG inside the PDF exactly as it is. Our two A4 scans at 300 DPI were JPEG files of 767,229 and 722,294 bytes, and the two-page PDF made from them was 1,491,215 bytes, just the two images plus about 1.7 KB of PDF structure. Merging PDFs works the same way: it copies pages across, so the merged file is roughly the sum of its parts.

That is good news for quality, because nothing degrades until you choose to compress. It also means the compression step has to do all the work at the end, and its settings decide whether the result is readable.

Two step orders, measured

Our set of documents: a colour mark-sheet scan and a grayscale ID scan (both JPG), a letter already scanned to PDF at 150 DPI, and a one-page certificate downloaded as a digital PDF with real text. We tried two orders to reach 200 KB.

Both finished well under 200 KB, and at 100 percent zoom the scanned text was equally readable in each. The difference is the certificate. The compressor redraws every page as a JPEG picture, so in Order 1 the certificate's crisp vector text became a compressed image and could no longer be selected or searched. In Order 2 it went in untouched and added only 1,064 bytes, because a text-only PDF page is tiny.

One side effect shows up in both orders: compressed pages come out with larger page dimensions than A4 (833 × 1179 points here), so Order 2's file mixes page sizes. On screen every page scales to fit the window. If the file will be printed, check the print preview and choose fit to page.

Step by step (the order we recommend)

1. Collect everything in one folder and name files in the order they should appear, such as 1-marksheet.jpg and 2-id-front.jpg.
2. Open Image to PDF, add the photos, choose A4 as the page size, check the order, and press the Convert button (for two photos it reads Convert 2 Images to PDF). Download the PDF.
3. Open Merge PDF, add that file plus any other scanned PDFs, drag them into order, and press the Merge button, such as Merge 2 PDFs. Download the merged PDF.
4. Open Compress PDF, choose Target Size, type a number a bit below your limit (190 for a 200 KB limit), click KB, and press Compress. The unit starts on MB, and a target of 190 MB would barely shrink anything.
5. Open Merge PDF again and combine the compressed scans with any digital PDFs such as downloaded certificates. Put them in the order the portal expects.
6. Check the final size in your file manager and open the PDF once to zoom into the smallest print before uploading.

When the limit is very tight

Three or four scanned pages fit comfortably in 200 KB. Ten pages will not look good at that size, because each page gets about 20 KB. Before lowering the target further, work through these:

• Leave out anything the notice didn't ask for, such as blank reverse sides and instruction pages.
• Crop scans to the paper edge before converting. A phone photo that includes the table around the document wastes bytes on wood grain.
• Photograph documents in good light rather than dim indoor light. Noise from a dark photo is expensive to compress and ugly when compressed.
• If the portal accepts separate uploads per document, use them. Each file then gets its own 200 KB.

Problems you might hit

• “is password-protected and was skipped” when merging: a downloaded bank or university PDF may be encrypted. Remove the password (you need to know it) and merge again.
• An image won't convert: unusual formats and CMYK JPEGs are re-encoded through the browser, and if that fails the image is skipped with a message. Re-save it as a normal JPG and retry.
• Pages in the wrong order: fix the order in Merge PDF before compressing, because every extra round of compression costs a little quality.
• Compression stops with a timeout: keep the tab visible while it runs. Browsers slow down background tabs, and the tool stops after 90 seconds.
• Photos larger than 20 MB each: the image-to-PDF uploader turns them away. Resize the photo first; you don't need 50-megapixel scans for a portal.

Frequently asked questions