How did you migrate your library exactly?

If you moved your Zotero data directory completely, you would have the exact same files. It's exactly the same as restoring from a backup.

But I'd guess that you actually did something wrong in the copy and simply synced to pull down your library from the server. You're at your storage quota online, so additional files wouldn't have been uploaded from the other computer.

See Transferring a Library to understand exactly what you need to copy from the other computer to get your full library.

I'm telling you — you either didn't copy the folder correctly or didn't have the files on the other computer. If you copied the entire folder to the correct location, you would have the exact same Zotero library on this computer.

There's nothing else we can tell you here. Obviously if you place the exact same files in the exact correct place and start up Zotero, you're going to see the exact same thing.

As someone just trying to figure out an issue that doesn't make immediate sense--that's why I'm on a forum in the first place--I'm a little bewildered by the aggressive tone here, although I appreciate the follow-up.

I've tried searching when Zotero attempts to locate a PDF, but the PDF name doesn't auto-populate in the search box, and the search that pops up either doesn't include text in the document or the document itself isn't on the computer.

I will probably just try to re-copy the folder over and hope that works.

I'm new to this so apologies if I'm mistaken - there seems to be 2 ways to attach pdfs to citations, either Zotero does it automatically and saves them in a default location (C:\Users\user\Zotero\storage\) or you can manually attach a pdf from one of your own folders. Could it be that the files in the default folder have transferred across but the ones you may have attached manually are pointing to other folders not on your new machine?

@dstillman, what I mean is that when Zotero can't find the PDF, it offers an option to Locate, but that search bar doesn't auto-populate with what Zotero has saved as the PDF name. I can see it and retype part of it from the File Information in the citation data, but so far I haven't had luck in trying to locate files that way. It's likely because they're not actually on the machine, but since I've yet to successfully search and find one, I don't know if it's absence or an issue with transcribing the file name.

@fazwardak thank you, this is helpful, and definitely a possibility. I don't *think* that it's an issue of manual attaching, because the documents I'm looking for were saved in the last year or two, and I haven't used the manual link in a long time.

If it is an issue of having linked to PDFs that are not stored in Zotero Library files, is there any way to systematically locate these, within Downloads or whatever folder they might be in? I'm assuming not and that I'd have to search one by one in my old computer.

And it's not linked files. You have about a dozen linked files created years ago and hundreds of stored files, many of which haven't been uploaded because you're at your storage quota. Presumably those are most of the files you're referring to.

There's nothing you would be doing for every file here. You either didn't copy the full data directory or you copied it to the wrong place. All you're doing is searching for a few of the PDFs — by 8-character folder name or part of the filename — to see if you accidentally placed them somewhere else. If you didn't, just try the copying from the other computer again. (And confirm that you actually have the files you think you have on the other computer.)