You'd have to say more about what the problem is, and we always need an example URL for problems with saving.
Make sure you're saving the actual remote http(s):// URL, not a local file (which you can just drag to Zotero). But on a supported site like WOS, you should be saving from the article page, not the PDF itself.
Make sure you're saving the actual remote http(s):// URL, not a local file (which you can just drag to Zotero). But on a supported site like WOS, you should be saving from the article page, not the PDF itself.