Verify image resolution

[mikepurvis]

In particular, images containing the text callouts— generally speaking you need ~300dpi to look okay in print. Alternatively, the Jackal manual handles this case by using tex output generated directly from Inkscape, so that the in-diagram text is still typeset text, rather than text in an image (admittedly, a more finnicky process).

cf. https://github.com/jackal/jackal-user-manual/blob/master/gen/battery-view.pdf_tex