PDF is a (per) Line format
Converting does not always make changes to that aspect without help.
Under the conversion options (at the start of a Conversion), You have Heuristic Processing.
There you have Un-Wrap Factor.
This is a bit fiddly (trial and error)
I prefer to just fix this in the EPUB editor S&R
(Sorry, but I use the Sigil editor for this as I started before Calibre added one. I adjust the class= as needed) The rest I craft as needed (not very common)
1) Join (line 2 starts with )Lower
2) Join (line 2 starts with )Upper
3) Join Honorifics
Code:
(Mr|Mrs|Ms|Dr|Prof)\.</p>\s+<p class="calibre\d+">([A-Z])