pdf

You cannot.

However, you can combine a sequence of actions that will give you that effect.

First, import the .PDF*. You can click File / Import PDF. This will take you to a webpage where you can upload your .PDF and it will return a MuseScore file. Open this MuseScore file and make whatever changes you need to using the MuseScore Studio program. Once all changes are made, export the file as a new .PDF.

* The built-in .PDF import that I described above uses an old (and basic?) version of the software (Audiveris, I believe) that performs this action. This old version often creates a score file with lots of problems. You may want to get your own software to convert .PDF to .musicxml/.xml to get a better result. Look around the Forums, I have seen three or four programs mentioned as giving much better results. One such possibility is simply installing a current version of Audiveris locally on your computer.

File -> Import PDF.

Your PDF file is sent to a website and Audiveris runs there, which then interprets the file.
The result is more or less good and depends on the quality of the original. In any case, you must be prepared for reworking! It delivers music xml files.
The Audiveris tool is also available for local installation. This gives a slightly better result as you can make corrections. Unfortunately, the tool is a bit difficult to use ...

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