You can start with a large flat bed scanner.
Mustek used to make one that had a platen size of 11" * 17".
If needed, you can scan a document with overlapping edges, and use a good image editor to combine the images into a single graphics file.
While I have not tried it with documents, some of the panarama programs should be able to combine multiple scanned images into a single file.
For blue prints and tech drawings, you can use a raster to vector conversion program to import the TIFFimage from the scanner into a standard CADD file.
Both Turbo Cadd (www.imsisoft.com) and Visual Cadd (http://www.tritools.com/) have built in raster to vector conversion programs.
Depending on the style of the maps, you could use the CADD program, or convert the scanned image to your graphic format of choice.
Unless the maps are specialized, I would consider converting over to one of the mapping software packages such as Street Maps, or Rand Mcnally.
Chas