This is what I've learned from printing out maps for other games, and taping the multiple sheets together.
Adobe Acrobat Reader has a nice 'Poster' mode to print out the map on multiple pages, with overlap so you easily tape the pieces together. This is what I did.
- In Tom Morin's article on page 3 of DftB44, he mentions the map has 1" hexes and is roughly 22" x 22.5".
- I opened ReesMap-final.pdf, then used Ctrl-P to open the print menu. I click on the Poster button under "Page Size & Handling", and I see Adobe reports the map is 25.5" x 33" and will be tiled across nine pages. 25.5"x33" is the size of a 3x3 array of 8.5"x11" sheets of paper, not the size of the image. It is centered in the array and has a large white margin around it. However, the image of the map looks about the right size but I want to be sure.
- I leave the "Tile Scale" at 100% and Print (using low quality and toner saver modes so I don't waste much). I measure across several hexes and yes, they're each exactly 1" across.
- At this point I could go to a commercial printer as @Zakopious wrote, tell them 22"x22.5" and to print the PDF at 100% scale. A D-size sheet of paper is 22"x34", but they may not be able to print exactly to the edge of the paper, so they may have to use E-sized, 34"x44".
- But if I want to print and assemble the map, I'll use the print menu. Poster is selected, and the default overlap is 0.005 inches. That's much to little; it'll look like no overlap to my eye. I change it to 0.25 inches.
- My printer can handle 11"x17" paper so I also use Page Setup to change the paper size to Ledger. Acrobat now shows it will be tiled across only six sheets of paper.
- I print, trim, and tape them together. It's not as nice as having it on one sheet from a commercial printer, but it's cheaper.
Do it once and you'll be an expert.
The reason I use the PDF, not the JPG version, is that while MS Paint can tile an image across multiple pages, it has no 'overlap' setting.