In limited circumstances, I use Google Docs to convert pdf files with straightforward, simple pdf files. I also use CloudConvert, an add-on to Google Drive. The latter works surprisingly well, even with fairly complicated documents. It is free for limited conversions, minimal cost for on-going bulk conversions.
I have been using Ubuntu Linux and various versions of Windows (currently 8.1) for three years now. I have three older pcs running 14.04 (between 2 and 4 gb memory) and one more up-to-date pc running Win8.1 (8 gb memory).. Hands-down, I prefer Ubuntu, even running on the older pc's. My Ubuntu "crashes," if you can call them that, are about 1 for every 50 windows crashes, including when I ran Windows 7. Network connections are much simpler and do not drop like they do with Windows. I could go on, but suffice it to say that if only there was a native Linux client for Google Drive, I would rarely use my Windows pc.
In limited circumstances, I use Google Docs to convert pdf files with straightforward, simple pdf files. I also use CloudConvert, an add-on to Google Drive. The latter works surprisingly well, even with fairly complicated documents. It is free for limited conversions, minimal cost for on-going bulk conversions.