Will USGS historical topo maps be made available in GeoTIFF format?
USGS does plan to publish GeoTIFF versions of the Historical Topographic Map Collection (HTMC, http://nationalmap.gov/
historical/). The design of a GeoTIFF product is currently being studied. Creation of these products may start in 2015.
Although USGS does not endorse any specific products, both commercial and open source software is available to convert GeoPDF to GeoTIFF. Such software includes Geospatial Data Abstraction Library (GDAL) open source translation utilities, Acrobat 9 Pro Extended, GNU Image Manipulation Program (GIMP; freeware that does not keep the georeferencing), Map2PDF, ArcGIS, ERDAS, Global Mapper, and Garmin G-Raster, and probably other software we are not aware of.
The FAQ at http://www.usgs.gov/faq/
categories/9797/3704 includes a reference to a USGS technical paper with more detail on GeoPDF-to-GeoTIFF conversion