The software is called LibreOffice. Can you imagine some offices actually sending invoices as pdf? And somebody actually created the pdf, you wish to fill. So maybe an Office-suite is software for them and you should just use a more simple program to fill your pdf.
Imho there is not much overlapping with existing topics. So it would be no advantage to include it. I don’t think there is an idea to include everything simple in LibreOffice, just because it is possible.
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(And if you’d know anything of the topic, you’d see it is not that simple, as there is more than one “standard” created by Adobe, and that is not even counting the forms, which are “impoved” by javascript…)