We would need an example PDF to say more — that's obviously not a universal problem. Provide a link or email a PDF to support@zotero.org with a link to this thread.
Make sure you're running Zotero 7 and have tested with all plugins disabled.
Sorry, this is not an uncommon problem. When opening four or five dissertations with hundreds of pages, Zotero's memory usage exceeds 1G and becomes stuck, and even the right-click menu becomes very slow. In addition, some operations are not responsive. I think this should be a performance problem of the PDF browser, but another PDF software I use (Sumatra) does not have this problem. However, third-party PDF browser software will make some functions of Zotero unavailable, so using a third-party browser is not a good choice. Sumatra is an open source software, maybe you can get inspiration from its source code.
@luoj1379: As above, make sure you're running Zotero 7 and are testing with all plugins disabled and Zotero restarted.
Memory usage exceeding 1 GB with multiple large PDFs open is completely normal.
Loading very large PDFs, particularly those with many or heavily compressed images, might be slow in some cases.
Performance problems just using Zotero while PDFs are open would not be normal, and as above, we'd want to see the PDFs that were causing this, with specific steps to reproduce it.
(Zotero is based on PDF.js, the PDF library used in Firefox. A native single-platform reader isn't equivalent.)
I was having similar issues and it turned out my institution had the 32-bit version in their software repository. Changing to the 64-bit version fixed the issue for me. Unless you're using a 20+ year old computer, there's really no reason to not have the 64-bit version.
You can see which version you're running by clicking Help -> About Zotero and looking just below the heading and next to the version number. It should say 64-bit or 32-bit matching the version you have installed.
If you're using the 32-bit version, I would recommend downloading and installing the 64-bit version to see if the problem persists.
Upgrade Storage
Make sure you're running Zotero 7 and have tested with all plugins disabled.
Memory usage exceeding 1 GB with multiple large PDFs open is completely normal.
Loading very large PDFs, particularly those with many or heavily compressed images, might be slow in some cases.
Performance problems just using Zotero while PDFs are open would not be normal, and as above, we'd want to see the PDFs that were causing this, with specific steps to reproduce it.
(Zotero is based on PDF.js, the PDF library used in Firefox. A native single-platform reader isn't equivalent.)
You can see which version you're running by clicking Help -> About Zotero and looking just below the heading and next to the version number. It should say 64-bit or 32-bit matching the version you have installed.
If you're using the 32-bit version, I would recommend downloading and installing the 64-bit version to see if the problem persists.