To expand on Michael Kazlow's response, the problem isn't caused by Windows, but rather how Microsoft Office applications format their text. The issue isn't only with Word, but also with every other Office application as well. Furthermore, it isn't a matter of whether you create the PDF using the Adobe PDF PostScript printer driver instance, but rather, when you compose the document while the Adobe PDF PostScript printer driver instance is the default/current printer within Word!!!
These applications format text using font metrics normalized to the resolution of the current output device. Thus, if you are displaying a document in Word and the current printer selected (usually the default printer you have selected in Windows when you start up Word) has a device resolution of 600dpi, the document is formatted with each character's space measured in units of 1/600 of an inch. If you change the current printer or print to a printer that has a different resolution set, Word reformats the document using font metrics based on the new resolution. In the case of the Adobe PDF PostScript printer driver instance, by default, the resolution is 1/1200 of an inch. Typically, more text will fit on a page with long text lines when higher resolution is used and less text will fit on a page with long lines when a lower resolution is used. If your default printer is a high resolution inkjet printer, you may see resolutions as high as 2400 dpi, for example.
Microsoft Office applications are also known to reformat pages based upon other metrics such as printable area.
These issues don't just affect PDF creation, but also printing to different devices yielding different line endings and pagination.
To further complicate matters, when you either Save as PDF using Office's own PDF creation facility or even Save as Adobe PDF using Acrobat's PDFMaker facility (part of Acrobat), Office uses yet a different mechanism to reformat the page, also yielding inconsistencies in line ending and pagination from what you see on the screen and/or in print directly from Word to a particular device. (We don't know exactly what mechanism Microsoft is using in these cases to cause the discrepancies.)
Users of Office and Adobe have complained to Microsoft about this general behavior for over 20 years and apparently it is not of any priority to Microsoft to resolve this.
- Dov