1. Create a new text document; 2. Make its page size A3; 3. File->Export As->PDF; 4. On Initial View tab, keep "Open on page" -> 1, and choose "Fit width"; 5. Continue exporting. => opening the resulting PDF in e.g. Acrobat Reader will show the first page not from top, but from its middle. Same thing would happen for "Fit visible". This is a wrong implementation from start, using /FitBH with a hardcoded vertical offset "g_nInheritedPageHeight" (A4 portrait hardcoded value) for "Fit visible"; and also using the same hardcoded value for /FitH (Fit width); when the actual vertical offset there must come from the actual page itself - or possibly be omitted, as the standard tells "A null value for *top* specifies that the current value of that parameter shall be retained unchanged". Code pointer: PDFWriterImpl::emitCatalog in vcl/source/gdi/pdfwriter_impl.cxx.
I can't reproduce when opening the resulting PDFs with GNOME Document Viewer, Okular, Foxit Reader, Firefox or Chromium, but my guess is that they don't support the parameter? See for example for pdf.js the lack of support for the embedded parameter: https://github.com/mozilla/pdf.js/issues/2757
(In reply to Stéphane Guillou (stragu) from comment #1) Missing features in PDF viewers are not handled here ;) Yes, you need a viewer that supports the discussed options of the OpenAction, as described in PDF 32000-1:2008 sect. 12.3.2.2 "Explicit destinations".