If the 120bpm tempo marker is at the top of your score, then double click on it and you will be able to edit the number. For better control, open VIEW> PALETTES.. or press F9.... Here is an excerpt from MuseScore about the requirements for a PDF file as related to the ability of MuseScore to Import the file: This is a free experimental service which attempts to convert your PDF sheet music to MuseScore (.mscz) files.
that's a BS response. I tried it, and you get a dialogue that allows you to indicate the number of semitones to transpose, or "transpose chord names;" the key selection box is grayed out.
Here is an excerpt from MuseScore about the requirements for a PDF file as related to the ability of MuseScore to Import the file: This is a free experimental service which attempts to convert your PDF sheet music to MuseScore (.mscz) files.
Musescore got very close but was missing a key feature. An obscure feature not needed very often. And in fact because the OP was doing some non-standard notation it might be kind of a questionable feature, but, of course, your engraving software should allow for as much craziness as possible.