Great section, looking forward for more
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Stig, I'm not sure if you are talking about the spreadsheet or the pdf document but you can download a free, open source pdf viewer (not to mention it is faster, smaller than any of its competitors) here
:
https://www.sumatrapdfreader.org/free-pdf-reader.html
Works also for ebooks & comics and remember were you stopped your reading.
Anyway, downloading the files have nothing to do with the way/sowtfare to open it, more linked to your browser's parameters.