For reference, I tried opening / importing the example with a variety of programs (e.g. GIMP, Xournal, Inkscape, etc.), and some didn't display the annotations, while others seem to "merge" the annotations so they were not editable.
I tried the script at:
and it at least gives numerous lines of the form:
Quote:
|
page: 1, D:20180202204930+03'00', type: poly-line , content: None
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Also, it summarized by saying it found 152 annotations.
So I'd guess there are PDF annotations of some sort contained in the PDF.
May be somebody with Windows (or some other relevant OS) and appropriate applications could test whether they are editable.