Brian,
A couple things could be happening. To know for sure,
click on the pilcrow mark on your standard toolbar (it is
the paragraph symbol that looks like a backwards capital
P). It should show you the formatting marks that cause
the line to break.
Oftentimes, text pasted from other non-word processing
programs (like PDF extracts or web text) has soft line
breaks (the format marks for them look like 90-degree
arrows). Hard carriage returns are those same pilcrow
marks.
If you want to adjust the length of the line, be sure
your rulers are visible (under View | Ruler) and then
look to see what the margin situation is like up there.
The line begins where you see a gray square on the left
and ends where you see a bottom triangle on the right.
When you have lines that break long before you get to the
right margin, it is because you have a soft or hard line
break.
The best way to address this kind of formatting is to do
a find and replace of the line breaks. Once you get rid
of them, you can let your default paragraph formatting
determine how long lines are. Open the F&R dialogue box
(control-F), and in the Find box, type, without the
quotes, "^p". Then replace with either nothing or a space
(depending on whether there are spaces between the words
already). You can go through and replace those extraneous
hard returns. do the same for soft line breaks with "^l".
For your purposes, I wouldn't trust doing a Replace All
(it could potentially enjoin all your paragraphs). If you
have a large block you want to make one single paragraph,
then you can select that paragraph and run a F&R on just
it.
Good luck.
Brandon
