I did this years ago with a piece of software and 2 cable HSD connections, but I don't remember what the software was and can't seem to find it again.
Anyway I would rather do it via something like pfsense rather than a windows box running for just that purpose…not too stable in comparison.

What I am more concerned about was the harder thing to do as I remember ... I want more upload bandwidth.

My wife may soon have the chance to work from home. Which is great...except that she needs to upload video files all day long to her company's servers through a VPN. So I am doubting that multiple connections for the same file will work well for her. She would need the opposite of a download manager.  Does this exist?
I am not as worried about the downloading of them as most HSD connections where we are are fast enough for that, but I wouldn't complain if that worked as well.

So if anyone knows a way to do this or has some recommendations of dual wan routers that have the aggregate bandwidth capability...please let me know.

Any info to help me out here is appreciated.

thanks