How to print/extract/save powerpoint notes to a text file on Mac

It's a little bit tricky. I'll take Mac Office ppt as an example

The principle is ppt -> pdf -> txt

1. open your ppt file
2. on the top bar click File -> print
3. in the printer window, make sure you select PDF as the output instead of real printers
    current option -> "PowerPoint" Layout -> "Notes"
    Click print
    You'll get a pdf with both the slides and texts
    But the slides are in image format so the texts in the slides won't be recognized and saved, so that you can only save your notes

4. go to http://pdftotext.com/
5. drop your pdf file to the upload box
6. click "Download All"

Alternatively
4. open the pdf using acrobat adobe
5. File -> Save as -> more options -> Text