Thank you for your feedback. It is this kind of messages that helps us explain the usage of our program and improve it.

The Docuflow messagebox that you indicate in your post says that the PDF file is locked by another process, and that must be closed in order to be able to write it. This is a limitation on the Windows file system, that must not be ignored. In order to write any file, it cannot be open/locked. In this case the PDF file mentioned in the box can be open nin a PDF reader or even in the Windows Explorer preview.

Docuflow at that stage has not crashed. To be more specific, Revit that hosts Docuflow, has not crashed. The program keeps is alive and the messagebox allow to click the button OK. 

In order to solve that in the future without the need to force Revit to close:

• Install Docuflow version 4.5. There is a additional button CANCEL that will stop the printing process in case you prefer not to close the PDF.

When trying to use docuflow i get an error message:

"Docuflow cannot save......please close the file and try again"....

After this message NOTHING works anymore and i have to force close revit (via taskmanager) in order to use revit and docuflow again.

Then docuflow works again for a short time and then theres the error message again.