Hi there, 

QuickBooks Online is an awesome place to store attachments such as files or receipts. I know how handy it is to be able to upload PDFs into your account, and I'd be happy to explain some troubleshooting steps that will help resolve this issue.

If you're running into this issue with the mobile app, try uninstalling and reinstalling it on your phone. This will help remove stored cache and install any updates. 

If you're using a browser, try clearing the cache and cookies in your browser to remove the stored Internet files that build up over time. These stored files can cause bugs in QBO and other sites. Here's how to clear them: Clear cache and cookies to fix issues when using QuickBooks Online. 

If the issue persists, try using an Incognito window in Google Chrome. This is a private browsing mode that operates separately from the main browser, and it doesn't get impacted by stored cache and cookies. Here's more information about that and how to use it: Browse in Private. You should also try using multiple different browsers to get things back on track.

If you're still having an issue uploading PDFs, please reach out to our tech support team so an agent can investigate this further. 

Have a great day.