(NOTE: ZotFile is no longer compatible with the Zotero 7 application. But it will work with Zotero 6.)
If you marked up comments or tags or notes on the pdf file from the Zotero application, the pdf file in your Google Drive folder will not be updated automatically. However, the markups are preserved when you open the Zotero PDF reader.
To save the markups on your PDF file in the Google Drive folder, you need to take a few extra steps:
Then the PDF file in your Google Drive Zotero downloads folder will be replaced with the one with those comments, tags, and notes.