Despite the influx of the digital/GPS world, I am still a paper map person.
Yes you can use the Toporama maps, but as you have done, they must be downloaded in bits then tiled together to make a complete but bigger map. Yes you can manipulate the final image to print it to a define scale. I have painstakingly added the UTM lines onto these downloaded composite images to aid this process, but the end result is a map with the Grid North on an angle.
If you are still wanting to invest your time with free on-line topo mapping, I suggest downloading the standard NTS 50:000 topo maps from:
ftp://ftp2.cits.rncan.gc.ca/pub/If you can, get your topo from the CANTOPO directory. I use the 50k_tif files.
These are higher quality images but
not very many NTS maps have been published in this format.
The CANMATRIX2 directory should have the complete NTS 50:000 topo series. Again I use the 50k_tif files.
After downloading the standard topos of my route (tiff files), I use Photoshop the crop, paste, rotate etc the topo area covering my route should it cover mutiple NTS sheets. I then bring the composite image into a graphic program (I use PowerPoint believe it or not) to annotate the map with paddle routes, portages, campsite location etc. This map is printable at 50:000 / 1 scale.
Then to produce map case size sheets, I digitally "chop" up my composite annotated route map into a series of sheets that are 9 x 6 UTM squares. I double the size of the image to make maps 25:000 / 1 for an easier read in the canoe with my failing old eyes.
Or.... buy a digital based topo with good color graphics display GPS.