It's true that the quote was published in a booklet titled Introduction to Outer Space well before it was used in Star Trek. You can see the entire booklet here. The relevant section is on page one:
The first of these factors is the compelling urge of man to explore and to discover, the thrust of curiosity that leads men to try to go where no one has gone before.
(Note that there is a cover page and introduction, so the quote is actually on the third "page" of the scanned copy above).
As far as Roddenberry having heard it, it wasn't Roddenberry who originally brought the quote to Star Trek. Roddenberry's original narrative didn't include the quote, but according to The Making of Star Trek, one of the writers, Sam Peeples, suggested it as the title for an episode (which became the second pilot episode). It was subsequently worked into the opening narration as well.
It's not clear exactly where Peeples originally read the quote. Besides the White House booklet, very similar phrases had appeared in several places beforehand, including a famous quote by James Cook (the explorer)
[not only] farther than any man has been before me, but as far as I think it possible for man to go
and this line from H.P. Lovecraft's novella The Dream-Quest of Unknown Kadath:
Carter resolved to go with bold entreaty whither no man had gone before
The pamphlet is typically considered the most likely source, though, for two reasons:
- The booklet was widely available, and would almost certainly have been read by people researching space travel at the time.
- The phrasing in the booklet is the closest to the phrasing on the show (though Lovecraft does use the word "bold" in his writing, though the rest of the quote is more archaic than the Star Trek version.)