|Be careful with the openpdfconverter, I've seen this one recently because it looked useful but there are a few suspicious things about it.|
Firstly, looking on the download page it mentions 'Youtube to mp4 converter'. Installing changes your search provider and homepage and mentions another program called Fliptoast. I have never gone past this point, but just be careful of what you are installing - try running in a sandbox (kaspersky) if you have one, & let us know if it does the job. Otherwise, wait for a few more positive opinions.
"I've always been mad, I know I've been mad, like the most of us..." Pink Floyd