I’ve got a 20-page scanned contract and a one-page addendum, and every merge I’ve tried makes the scan look blurry. How can I combine two PDFs without losing quality?
The blur usually means the tool is recompressing the scan while merging, so check its settings for image quality or downsampling and set that to none or highest. Honestly the easiest fix on a Mac is Preview: open one pdf, drag the pages of the other in, save. It keeps the original scan untouched.
You cannot fit a 20-page scan into 250kb without ruining the quality, which is why your merges look blurry. I learned this the hard way when combining my bakery invoices. One tip is to paste the original scans into a blank Word document and save it as a PDF. Just avoid compressing the colour settings if you want the text to actually be readable.
I had this exact trouble with scanned insurance forms getting blurry after merging. What worked for me was using PDFcap, as it stitches the pages together without re-compressing the scans. You just drop both files into the merge tool on pdfcap.com and download the combined document.
Had the same thing last month with a scanned lease. In my experience the blur usually comes from the merge step resampling images, not the actual scan. On a Mac, Preview can combine PDFs by dragging thumbnails without recompressing. On Windows I would try printing both to the Microsoft Print to PDF, which sometimes preserves quality better than online mergers.
@SneakySteel Microsoft Print to PDF worked on my old laptop too, no blur. Not sure if it’s the same on Mac. Just check page order, it does one file at a time.
@Emily.7 On Mac, Preview is the safer equivalent: open the first PDF, show thumbnails, then drag in the addendum pages and save. I’d avoid Print to PDF if possible, since it can rasterize pages and quietly reduce scan quality.
I usually merge the original PDFs directly rather than printing or exporting them through another app. In Acrobat, PDFsam Basic, or Preview on Mac, use the combine/merge tool and keep any “compression” or “optimize” option off. The scanned pages should stay exactly as they are; if they get blurry, the tool is likely re-rendering them instead of just joining the files.
Merging on its own shouldn’t blur anything, the problem is usually recompression happening during the merge step. Try PDFsam or pdftk, they just stitch files together without touching the images. What DPI did you scan at? That matters more than which merge tool you pick.
@wallabies I scan contracts at 300 dpi in greyscale, then merge with Preview on Mac, letting it just join the pages. Merging alone never blurred mine, it was always a resave step that recompressed. What dpi do you use for scans?
try merging without any compress or optimize option on, thats usually what blurs the scan. i use pdf24 on windows and it just concatenates the pages as-is. not sure if its the same on mac, preview can work if you combine then save without reducing quality.
Honestly, if the scan goes blurry after merging, the tool is recompressing pages instead of just stapling them together. I see this at work all the time, and I usually point people to PDF24 because it leaves the image data untouched. With Acrobat, just make sure the reduced file size option is off. If it still looks soft, the scan itself was probably low DPI to begin with.