Using the tool
Paste on the left and the joined text appears on the right. Replace breaks with turns each break into a space, a comma, or nothing at all.
Keep paragraphs is the setting most people want for a PDF. It removes the breaks inside a paragraph and leaves the blank lines between paragraphs alone, so the structure survives and only the hard wrapping goes. Extra spaces collapses the double spaces a join leaves behind and pulls stray punctuation back against the word before it.
There's no way back. Nothing records where the breaks were, so swap is switched off.
Why pasted text arrives broken
A PDF has no paragraphs. It stores glyphs at coordinates, and a line of text is a row of glyphs that happen to share a vertical position. When you copy, the reader reconstructs a text stream and inserts a break at the end of every visual row, because that's the only structure it can see.
Email does it on purpose. Plain text mail was specified with a line limit, and RFC 5322 still recommends no more than 78 characters per line. Clients hard-wrapped outgoing mail to hit it, so a forwarded chain arrives pre-broken at whatever width the original sender's client used.
Either way the breaks are real characters in the text, not a display choice. Paste that into a document set to a different width and the lines end in the wrong places. Removing them gives the text back to whatever is displaying it.
What gets lost, and what to check
Joining is lossy in one specific way worth watching for. A hyphen at the end of a line may be a real hyphen in a compound word, or it may be a typesetter breaking a word across lines. This tool leaves both alone, so a word split that way comes out with the hyphen still in the middle.
Scan the result for those before you use it. The other thing to check is a list: bullet points are separate lines with meaning, and joining them into a paragraph destroys that. Use Keep paragraphs, or pull the list out first.
Related conversions
Text rescued from a PDF often needs its capitals repaired too, and the sentence case converter does that in the same two boxes. If the text arrived percent-encoded out of a URL, decode it first with URL decode.
Stray invisible characters survive a join and cause trouble later. Paste a suspicious stretch into the Unicode converter to see exactly what's in it.
Questions
How do I remove line breaks from text?
Paste it above. Every break becomes a space by default, and the result is one flowing block you can copy straight out.
How do I keep my paragraphs?
Choose Keep paragraphs. Blank lines between paragraphs are preserved and only the breaks inside a paragraph are removed.
Why does text from a PDF have a break on every line?
A PDF stores glyphs at positions rather than paragraphs. The reader has to guess where lines end, so it puts a break at the end of every visual row.
Can I undo this?
No. Nothing in the joined text records where the breaks used to be, so keep your original if you might need it.