A great feature in Automate PDF creation dialog box is Append.
Append is a term similar to merge, however, it means combing the newly-created PDF file to the end of an existing PDF file. If the target PDF file exists, no matter which option you choose in Automatic Save, the target PDF file would not be overwritten, instead, the content of your newly-created PDF file would be appended to the target PDF file. Even Save-As-PDF file dialog is chosen in Automatic Save, you would not be asked to confirm whether to overwrite the target PDF file or not, the new content would be merged into the target PDF file at the very end.
