I am downloading FreeBSD 7.2. Is the Doc CD necessary? (I am downloading 3 CDs and not the DVD).
No, you don't need it. To install the system, it's enough to have CD1 (even without internet connection). Then you can fetch the ports and download the latest software, because the software on CDs/DVDs is outdated anyways (depends on your needs). If you just want a working system, you can grab the CD1-CD3 or the DVD with all of the yummy software.