Why does text copied from a PDF break at every line?
PDFs store a hard line break at the end of every visual line. Turn on "Join lines into one paragraph" to stitch those lines back together with single spaces.
Does it handle tabs and non-breaking spaces?
Yes. Tabs, non-breaking spaces (NBSP) and full-width spaces are treated as whitespace, so they are collapsed or removed along with ordinary spaces.
Will this change my word count?
Word count stays the same unless you remove all spaces. The character count usually drops, and the tool shows the before and after numbers under the result.