Recently, I was involved with a fairly big mail merge exercise. I had to create and print individual letters for 6000+ employees. No big deal, right? It's fairly standard mail merge project.
But, knowing that many employees will misplace or discard the letters and come seeking copies, I wanted to create PDF copies of each letter, stored on the company network, and with a unique file name comprised of inter alia the employee's cost center number, employee number, department name and job title. Again, no big deal but my outdated version of Microsoft Office wasn't going to do it, so I used LibreOffice 4.2.
It should have been plain sailing, but I experienced crash after crash, as LibreOffice just rebelled on both the Windows and Linux operating systems. And when it worked, it was SLOW.
Well, eventually I found the problem. It was small, and not something I would have thought of straight off, but with hindsight I guess it makes sense. MAKE SURE YOU ARE NOT USING EMBEDDED FONTS IN YOUR MAIL MERGE TEMPLATE!
Once I turned off embedded fonts, LibreOffice did its stuff quickly and efficiently. I was able to produce mail merges of all the letters in both the MS Word .doc format and PDF format. Printing worked smoothly, and the company's printing unit handled the inserting of the printed letters into window envelopes.
If you haven't tried it yet, you can check out LibreOffice here: https://www.libreoffice.org/