I just tried to import two notes from Evernote. Both of them are PDF files. One was imported, but the other one was not. Here’s the error message that I get from Joplin:
These items will remain on the device but will not be uploaded to the sync target. In order to find these items, either search for the title or the ID (which is displayed in brackets above).
neatworks4_guide2.pdf (c147da5bce12859c2f8a81bea94742fe) could not be uploaded: Resource exceeds OneDrive max file size (4MB)
I didn’t know that I had a 4mg limit on Onedrive. Is this a limitation of Joplin or Onedrive?
It’s a limit of OneDrive, unfortunately third part apps that access OneDrive (like Joplin) are limited to 4MB per file.
@cloaked that also means there's nothing you can do, as long as you're using OneDrive to sync. 
(I've switched from OneDrive to NextCloud because of that; hadn't tried the others so can't give you more info.)
Yeah, I’m going to need to do some research on NextCloud. Thanks.
You could also maybe try DropBox or some such thing that has a free version. Dunno how well that works, however. (More specifically, whether it does have some annoying restrictions, or not.)