If combining or printing PDF pages in Foxit PDF Editor and you receive an error stating '\\?\C:\.. file does not exist' that is due to a Windows file path name limitation. If the file path is over 247 characters, Windows will not be able to find the file as it exceeds the max path filename length:
In the Windows API, the maximum length for a path is MAX_PATH, which is defined as 247 characters. A local path is structured in the following order: drive letter, colon, backslash, name components separated by backslashes, and a terminating null character. For example, the maximum path on drive C is "C:247-character path string plus null.
If you are unable to get 247 characters in your file path, Windows 10 offers the ability to extend the Windows default max path length. In order to edit the Windows LongPathsEnabled key, simply edit the below registry entry:
1. Start the registry editor (regedit.exe)
2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem
3. Double click LongPathsEnabled
4. Set to 1 and click OK
If you continue to get the error after the limit has been raised, please shorten the path to fit the Windows maximum of 247 characters or contact Microsoft support regarding OS limitations as this is not a Foxit PDF Editor issue.