Google Apps Script has strict limits for @gmail.com users and newly created G Suite accounts.
For example, Google limit for @gmail.com users and newly created G Suite accounts on spreadsheet script is set to around 6 minutes / execution. You can send to no more than 100 email recipients / day.
The more data you have to process the longer document generation will take. Converting generated documents to PDF can take more than twice as long as generating a Google document.
Google Apps Script Current limitations: https://goo.gl/cbfe44
Google Apps Script Current quotas : https://goo.gl/pJm4JI
Gmail sending limits (not to be confused with Google Apps Script limits): https://goo.gl/nUfdLx
If your document generation stops at 50 please consider the following choices:
1. Click GENERATE again and again until you get all your generated documents. Our row status management allows you to run the process as many times as necessary.
2. Choose the option GENERATE > Every hour. This will allow you to do other work and come back when Doc & Mail Merge has finished generating your documents. If you close your computer while Doc and Mail Merge is generating your documents every hour, don't forget to refresh your spreadsheet when you come back to see all your generated documents.
3. Move rows marked "Done" to another sheet
4. Insert a column on your current spreadsheet and sort the rows so that those that are marked "Done" are at the bottom of your spreadsheet. ie. G Merge will first scan rows that need to be processed.
5. Subscribe with a seasoned G Suite account (>6 months) to benefit from extra Google Apps Script quotas like 30mns runtime + 1500 email recipients / day
The script will scan each row during document generation, including rows that are already "Done". If you have 1500 documents to generate, document generation will slow down the further the add-on gets down your spreadsheet. For this reason we recommend that you have no more than 500 rows per spreadsheet.
If you get a message "DoneFile not created", delete the wording "DoneFile not created". Your document will get generated the next time G Merge is running.
Time-driven triggers cannot run more frequently than once per hour. See limitations set by Google here.