Your print area is limited by the paper size and plotter/printer limitations. It is possible to tell AutoCAD to print to the edges of the paper but most plotter/printers cannot print to the edge. You need to determine the limits (and location) of the printable area of the printer and use those dimensions for your title block. Luckily AutoCAD does show this area but you cannot snap to it as you have found. You can use the length and with of the printable area to draw your title block and manually align that with the visual representation of the edge of the printable area.
When printing to printable extents on a plotter/printer you might run into trouble with elements that are on the edge getting partially cut-off especially lines parallel to the edge might not show their assigned linewidth. You will have to account for that, too. Most people avoid all this by giving themselves a margin of error (pun intended).
Rob
Drafting is a breeze and Revit doesn't always work the way you think it should.