The apparent cause is that the font used in the original is not available in the web app so a substitution has been made in order to display the document. Although very similar in appearance the metrics of the 2 fonts are slightly different. That causes the spacing to be altered somewhat which forces the web app to generate more lines.
The trickle-down effect is that the last paragraph comes close enough to the bottom margin to prevent the entire paragraph from fitting on that page. Therefore, the last 2 lines of the paragraph are forced to the next page due to Widow/Orphan Control.
Try changing the font to a Microsoft font [e.g., Cambria, Georgia, etc.] which is available in both the desktop software & the web app to see how the flow compares.
BTW: The only indentation is the last paragraph which is the same in both screen shots, so I'm not sure what you are referring to.