Hello there, phoneixarising.

Thank you for sharing your suggestions for other users here in the QuickBooks Community. Affected users may try this out to isolate the problem with attaching a document.

For additional insights, I'm also adding the article I recommend in case someone needs it: QuickBooks Attached Documents: FAQs and common issues.

Thanks for dropping by, the QuickBooks family wish you a wonderful rest of your day.

I just require simple instructions on how to attach pdf to invoice. I am getting an error 

Hello there, Cybertranz.

Let's perform some steps to resolve this and gets you able to attach pdf to invoice. Before doing so, may I know the exact error that you've encountered? Any additional information is appreciated.

Meanwhile, you can run a clean install of QuickBooks to resolve this. 

Here are the steps:

• Make sure a clean install is right for you.
• Gather info and back up your data.
• Uninstall QuickBooks Desktop.
• Use the QuickBooks Clean Install Tool

• Reinstall QuickBooks Desktop

Each of these steps have sub-steps. To see them, kindly see this article: Clean Install QuickBooks Desktop.

If the same thing happens, you may be having an issue with your company file. You can run a rebuild data and verify data utilities to resolve data damage. 

Let me know how these steps work for you. Just leave a reply below.

Same thing happened to me.  I went through  all the reinstall too.  It was a simple fix, rename the folder you are attaching your .pdfs from.  I had a folder I used on my desktop named Temp.  I changed it to Stuff and it is working fine now.  

QBO throws this error when an ampersand character (&) is used in the filename.