DVD Shrink is a free download. Google "DVD Shrink" and it will direct you to several download sites. I think I downloaded from the official site, but it has been so long I don't remember for sure. It doesn't have very good instructions, being a free product. A lot of commercial DVDs are bigger than 4.7GB, which I think is the standard size for writable DVDs, so DVD Shrink compresses the files to under 4.7GB. Or you can re-author the DVD, splitting it into 2 files for later burning to 2 dvds, but you lose the menu features when you do this. If your DVDs are DVD-R, they are likely not larger than 4.7GB.
Nero is quite easy to use. You can burn cds, dvds, bootable dvds, iso files, etc. I am not sure of the cost, as I got the Nero cd with a cd/dvd burner I bought for my pc years ago (it is just the basic version, I don't know what other features the higher end version has).
Googling "Nero Burning ROM" it looks like it is available from Nero as a free download. What was Nero Burn Lite is now called Nero MediaHome.