Merging & Organizing
How to Combine Scanned Documents Into One PDF
Turn a pile of scans and photographed pages into a single, tidy PDF — in the right order, the right way up, and a sensible size.
Scanning rarely produces the file you actually want. You end up with a folder of separate PDFs, some photographed pages, a few blanks and at least one page sideways. Here is the order of operations that turns that into one clean document.
The sequence that works
- 1Convert any photos to PDF first, so everything you are working with is the same format.
- 2Rotate the pages that came out sideways, page by page rather than in bulk.
- 3Remove blank pages, especially the backs produced by duplex scanning.
- 4Merge everything, dragging the files into the correct reading order before you run it.
- 5Run OCR if you need the text to be searchable.
- 6Compress last, once you know the document is otherwise finished.
Getting photographed pages to look like scans
Phone photos of documents come out with the page at a slight angle, uneven lighting and a background of desk. Most phone scanning apps will crop to the page edges and flatten the perspective before you export — use that mode rather than the plain camera, because no PDF tool can recover a page edge that was never captured square.
If you already have plain photos, convert them anyway and accept the result. A slightly crooked page is legible; a re-photographed one costs you an afternoon.
Why scanned PDFs get so large
A scan is a full-page photograph. At 300 DPI in colour, one A4 page is several megapixels, and a thirty-page document easily passes 50 MB. Two settings do most of the damage:
| Setting | Effect on size |
|---|---|
| Colour instead of greyscale | Roughly triples the data for a black-and-white original |
| 600 DPI instead of 300 | Roughly quadruples it, with no visible gain for printed text |
| Lossless output instead of JPEG | Can multiply size several times over |
For ordinary printed text, 300 DPI greyscale is the sweet spot. If the scans already exist at higher settings, compression will bring them down.
Making the finished document searchable
A merged scan is a stack of pictures. Searching it finds nothing, because there is no text in the file — only images of text. Running OCR reads the images and adds an invisible text layer underneath, so the document becomes searchable and copyable while looking exactly the same.
OCR is worth doing on anything you might need to find again: contracts, receipts, correspondence, anything going into an archive.
Do it now
Merge PDF
Combine multiple PDFs into a single file. It runs in this browser tab — your file is not uploaded anywhere.
Open Merge PDFFrequently asked questions
How do I combine scans that are separate PDF files?+
Merge them. Convert any images to PDF first so every input is the same format, then drag the files into reading order before merging.
Should I OCR before or after merging?+
After. One OCR pass over the finished document is faster than OCRing each fragment, and it produces one consistent text layer.
My scanned PDF is 80 MB. Is that normal?+
For colour scans at high DPI, yes. Compress the finished file — scanned documents typically shrink by 60–90% with no visible difference on printed text.
Can I fix a crooked scan?+
Only by rescanning. Rotation corrects 90-degree steps, not the two-degree skew of a page that went through the feeder at an angle.