It is time-consuming to print multiple Google Docs created using Mail Merge add-on one by one. This article describes how to combine multiple Google Docs from Google Drive into a single PDF file using the free web app PDF Merge before printing the PDF file.
Open PDF Merge in your web browser, which is a free web app that can merge multiple Google Docs into a single PDF file that can then be printed.
Click on Select Files from Google Drive.
Select all of your Google Docs that were created using Mail Merge add-on, and then click on Select.
Click on Merge.
Click on Save PDF to Google Drive.
Click on Show PDF in Drive to open the merged PDF file, which can then be printed.