The cause of this discrepancy lies in the difference of definition of what constitutes the printable area.
In Writer, page margins define an absolutely no-print zone. This means header and footer areas are subtracted from the space betwen the margins.
In Word, page margins define the area where main text will flown and laid out. Header and footer are located outside this “composition” zone and are positioned inside the margins.
Though the doc(x) import filter does its best to “translate” the definitions, there are cases where it fails. Consequently, the usable height in the page is smaller in Writer than in Word. If your page content is quite “tight”, the last few lines may spill over to next page.
Now the question is: is your manual page break really semantically meaningful? Is your unit of formatting the page or paragraphs? A page break only to create “vertical spacing” should be replaced by some parameter in a paragraph style, so that the style automatically decides whether a certain amount of vertical space should be use (mid-page occurrence) or a page break (bottom of page occurrence). If you design a page-based document, a better tool is a DTP application like Scribus otr Quark XPress®.
Meanwhile, the workaround is to adjust top and/or bottom margin in the page style. BEWARE, however, if you work collaboratively in a mixed LO-M$ team. It could be much better to defer margin adjustment until the final proof-reading to avoid transient conversion issues.
And, as usual, decide which application is the master reference: Word or Writer, to store the document in the appropriate format (.doc(x) or .odt).
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