I found this offer while doing website promotion for my site, The offer was One Time Bookmarking Packages Duration Price  50 PR 6 and above Sites (30+ PR 7 & above Sites & 20 PR 6 Sites) Could someone explain what this company if offering. This is new to me and I don't understadn what they will do if I pay them. Is there any advantage or disadvantage to outsourcing social bookmarking the way they are offeirng to do i?,
I guess you are paying for time. You can really do this manually, and plus some of these sites are probably no-follow so you won't get link juice for SEO.
"50 PR 6 and above Sites" means they will submit your site to 50 social bookmarking sites which have a PR of 6 or higher. As blogaboutnothin mentioned, not all of these sites would be dofollow sites. When you submit to nofollow sites, you don't get SEO benifit, but only traffic benefit. I often buy such services, but I prefer to submit to only dofollow SB sites. DP doesn't permit buying/selling social bookmarking services, but it is permitted on my other forums.