provide a downloadable, georeferenced image (pdf or ...) that I can save to a mobile device and import into an app such as PDF maps
Great! I got the georeferencing all done, but my data is still "stuck" on the website. I know I can download the kmz and the wld files, but I don't think that will help in using the original image/pdf with apps such as PDF Maps, which on android, can import georeferenced maps.

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Will1327 commented
When selecting a backpack, the first step is to measure your torso length. To do this, use a tape measure to measure from the base of your neck to your waistline. You should then add two inches to this measurement. This will give you the approximate size of backpack you need https://backpackfocus.com/best-convertible-backpack-2023/