Problem:
After pasting a file name from the clipboard into the Win2PDF file save Window, the application crashes or freezes when clicking the "Save" button.

Solution:
This is a known problem that isn't unique to Win2PDF, and we don't currently have a solution. Here are reports from users of other products with the same problem:

https://social.technet.microsoft.com/Forums/office/en-US/da64e0e8-ec5e-4b7c-8581-8238d6d93734/outlook-2010-freezes-when-pasting-text-from-email-into-filename?forum=outlook
https://forums.adobe.com/thread/1048202
http://www.dopdf.com/forum/dopdf-freezes-when-pasting-text-into-filename-field-of-save-pdf-dialog-box-t3133.html
https://bugzilla.mozilla.org/show_bug.cgi?id=647400

The issue is related to the focus of the pop-up Window. The pop up sometimes appears without being the focus, so the paste won't work because Windows can't determine the active window. Clicking on the save window to activate it before performing the paste may work around the issue.

You may be able to use the Win2PDF auto-name feature of Win2PDF to automatically name the PDF file and skip the Win2PDF File Save window. You could also rename the PDF by copying/pasting in the Windows Explorer after it has been created.