win2pdfd.exe append "file1" "file2" "mergedfile"
Where “file2” is appended to “file1” and the combined PDF is saved to a newly created “mergedfile”. If there is an existing file named the same as “mergedfile”, it will be overwritten. To prepend, swap file1 and file2.
Any file names that contain spaces must be enclosed with quotation marks.
Returns 0 on success, and a Windows system error code on failure.