I've had this issue for some time now, and it's starting to really annoy me. I've tried so many things I've found online, and nothing works. When I print a scanned PDF (whether or not it's sent by someone else or I scan it myself (different scanners)), I get random little grey boxes around the page. I just tested it myself - I got a blank sheet of paper and wrote something on it, then scanned and printed it, and it's a great example. It's not always this bad, but bad enough to be frustrating. Any help will be much appreciated!
So the boxes only show up when printed? can you upload a sample pdf? I suspect there are some 1% image areas (AKA scum dot) in the pdf and your printer is showing them a bit darker. Do you have an option to print as BW (not gray)?
Yeah, my guess is that those are scanned PDFs, and those artifacts are the result of scanning not just the text, but the paper itself. If you have the option to scan in Black & White instead of grayscale, give that a try to see if gives a better result. Another thing to try (can be labor intensive) is to see if you can select those gray boxes in edit mode to see if they can be deleted.
Unfortunately, deleting the boxes isn't an option, because they come up behind text as well. Also, I need to scan in colour (a requirement from clients). However, I don't print in colour.
I believe the boxes are caused by your printer converting an rgb dot into black, which is probably darker than 1%. Try converting a copy of your pdf to BW using a preflight profile shown in my screen shot, this should reduce or eliminate the boxes. Tools> Print Production> Preflight> Fixups (blue wrench icon).
I don't have the pro version of Adobe (no print production available).
OK, you could also convert it using Photoshop, but I assume you don't have that either. I don't have any other suggestions for you. I have attached your pdf, converted to BW with the preflight, I'm curious to see if it prints for you without the boxes, as this information might help someone else with the same issue.
When I printed by directly clicking your BW file and printing from the browser, it came up better, but instead of the boxes, it has little dots in square formations. When I saved it to a folder and printed through Adobe, it printed the same (with the grey boxes). The same happens in another PDF viewer. I've attached two pics of the dots (your BW doc printed from browser) and one with the grey boxes (your BW doc via Adobe). Thank you
I printed the BW pdf on my color printer and I also see a very faint (almost invisible) tint in the background, If I select the option "Print as Image" (under advanced settings) there is some improvement, if I use photoshop to remove all tone below 5%, the background is white (pdf attached), you could probably use any image editor to do the same.
I suggest you check for any print driver updates (Google the printer name and model number) then download and install them.