The nice thing about the store.usgs.gov site is that you can cache pdfs for maps in your area and then just print them yourself later. The thing that gets people with this, however, is that the underlying size of these maps is the standard USGS map sheet size, much larger than 8-1/2" by 11". What I suggest to actually print subset chunks is to not use the "poster" approach --- which gets you typically 9 sheets of paper to cut and paste. Instead:

(1) Open the .pdf file with the free Adobe Acrobat reader; if you don't have the Acrobat reader installed, it's readily available via web search, just follow instructions to download and install it
(2) use the ‘+’ or ‘-‘ buttons on the toolbar and use the horizontal and vertical slider bars to size and position the current view of the map to show just the subset that you want
(3) On the 'file' menu item, select 'print'
(4) Under 'Page Sizing & Handling' select the 'Actual Size' radio button, and then higher up under 'Pages to Print' click first the 'More Options' line and then click 'Current View'.
(5) Practice with this, playing around with with the sizing and position controls until your “current view” is the proper subset of the map that you would like to print.
(6) Before actually printing, consider clicking on the printer 'Properties' button towards the top of the print dialog box and make sure that you’re printing in color and that the quality setting is set to ‘high’.

Suggestion: After printing out the map subset(s) that you want and before zooming in or out from that same view, scroll down to the bottom of the map and consider also printing out (also as 'current view') the portion that includes the map scale and other legend data at the bottom of the pdf map sheet.


Now, all that said, an easier approach is to go to www.mytopo.com. From there:
(1) Scroll down and look at the lower right of their home page and under "Free Browsable Online Maps" click on the link that says "Start browsing maps"
(2) Left click on the map itself and drag it around, and use the zoom control to the left to zoom in on where you want. (3) When you’re reasonably well zoomed in, look at the upper right of the map to see three adjacent buttons: ‘Map’, ‘MyTopo’, and ‘Hybrid’. Click the ‘MyTopo’ button.
In a few cases, it's been reported that the screen changes to grey here and nothing else is possible; if this is the case for you, stick with the pdf approach via store.usgs.gov
(4) Continue to zoom and scroll the topographic view until what’s showing includes just the part that you want to print. You will need to have an idea of the area that you'll be traveling in to get all of the relevant parts; look at your trip description to find clues about that. Some practice at this will certainly help.
(5) Now towards the bottom of the web page, look for the line that says: “Print from your computer: Landscape | Portrait”. Again, a sense for where your trip will take you will suggest whether portrain (taller than wide) or landscape (wider than tall) will be a better choice.
(6) The result will be a new browser window containing the map portion to be printed. Look this over, and if it's what you want, then use your browser controls to print.

This process is faster/easier because there's no download, you just go directly to the map you want, zoom in until you've got about what you want to print. However, if you cache pdf's on your hard disk, then over time it's probably about as fast and needs no internet access (and the web sites can change in future and you won't care).

Another benefit to the pdf approach is that you can scroll down and print out legend (bottom of map) data; mytopo.com provides very little of that.

Suggestion: however you go, make sure that you're printing in color, and consider changing your print default for this map to be a high quality image in case that's not the norm for your printouts.
If you can't fit your entire trip easily on one such printout, do it multiple times to print out multiple pages.

Tip: use scissors to slightly trim off whitespace margin to slightly shorten the printed pages to fit in a gallon ziplock as an inexpensive, waterproof mapcase.

I really don't understand why people buy paper maps --- it boils down to simple ignorance, I suspect. If it turns out there is a yet-easier or otherwise better approach, I will appreciate in turn if someone will help lift my ignorance a bit further!