Adobe Reader Continues To Run ...

I have Adobe Reader XI on my computer. It was a download, but I don't remember where I downloaded it from. Anyway, whenever I view any scans, files, etc that are opened with Adobe Reader, the Adobe Reader seems to continue running even after I close it. I always know when this is happening because I can hear the fans speeding up and a small warning appears on my screen that basically reads "High CPU usage by Adobe Reader" even though I'm not using it. I have tried changing the compatibility settings and running my anti-virus, but neither seem to solve the problem. The only thing that seems to work is restarting my computer. Of course, the next time I use Adobe Reader the problem reappears. Do I have some type of virus? Do I have a defective download version of Adobe? Should I uninstall the program and just download it again from a different site? If I do uninstall the Adobe Reader will I lose the files that are opened with it?

Thanks in advance.

If you are willing to use a different program there are free alternatives to Adobe Reader for viewing PDF files.
I've been using Foxit Reader for years, it works well for me and have not had any problems with it.
Better than Adobe PDF Reader and Acrobat

If you have the Adobe file you downloaded, you can submit it to VirusTotal for scanning.
This will scan the file with many scanners, to see if any malware is found.
https://www.virustotal.com/

You should not lose any of your PDF document files if you uninstall Adobe.
You should always create backups of all your data and Backup Images of the "OS".

I've seen where Adobe Reader can cause performance problems if the Client program and a Browser have PDF files open at the same time.