Its App Store description puts it in as many words: “It changes text that is already in the PDF, one line at a time. It does not add text boxes, move text from one line to the next or reflow paragraphs.” So a paragraph is edited as the lines it is made of, each one on its own.

Why can’t a PDF paragraph reflow?

Because the page draws lines, not paragraphs. A word processor keeps a paragraph as one run of text and works out the line breaks each time you type. A PDF keeps the result of that work: each line is drawn at its own position on the page, often in pieces, and in the drawing instructions nothing ties the lines together. A tagged PDF can mark a paragraph for screen readers, but that tag does not change where each line is drawn, so nothing rewraps. The paragraph you see is an arrangement of separate lines. How a PDF stores text shows what the file holds.

So an editor that rewraps a paragraph is not editing the lines it found; it rebuilds them, with new breaks, new positions and often new spacing. PDF Textfix does the opposite. It changes the words of one line and checks that every other character on the page stays where it was. When new text would collide with the words after it, it refuses the edit and says why: “The edited text runs into the text after it on this line, such as the next column, and would read as part of it.” When those words belong to another line, it adds: “Moving the rest of the line does not make room, because that text belongs to another line.”

What can I change in a paragraph?

More than the “no” suggests, as long as each change stays inside its line:

  • A word for a word of about the same width. A wrong name, date, figure or spelling: how to fix a typo in a PDF is the usual case.
  • A shorter word. The lines below stay put, and Shift Rest of Line (⌃⌘R) closes the gap it leaves in its own line.
  • A slightly longer word. When it would run into the words after it on the same line, PDF Textfix moves them by the change in width and says so in the bar. The line grows to the right, so it needs free space there.
  • Several lines, one after another. Tab applies an edit and selects the next line, and Return opens it, so you can reword a paragraph line by line, keeping each line about as long as it was.

Each line you change counts as one line edit.

When should I go back to the source document?

When the change alters where the lines break: a new sentence, a cut that should pull the next lines up, or a rewrite of most of the paragraph. Edit the Word, Pages or InDesign file the PDF was made from and export a new PDF; the layout program does the rewrapping, which is its job.

Without the source, converting the PDF to a word processor document gives you paragraphs back, at the cost of the layout: fonts, spacing and page breaks are rebuilt rather than kept. How to edit a PDF in Word or Pages says what changes.

What kind of tool rewraps a paragraph?

A full PDF editor that edits text as boxes or blocks rather than as lines. Two of the editors this site compares, in their vendors’ words:

  • Adobe Acrobat edits text in boxes: “When you resize the text box, the text reflows within the box, but the font size remains unchanged.” Its font rule is the trade-off: “To edit text using a specific font, you must have that font installed on your computer. If the font isn’t installed but is embedded in the PDF, you can only change the text’s color or size.” PDF Textfix and Adobe Acrobat sets out the rest.
  • PDFgear works the same way: “PDFgear recognizes PDF text as multiple text blocks, and you’ll need to work with them one by one.” Its guide adds: “Use Enter on the keyboard to start a new line and type in text in the same font.” PDF Textfix and PDFgear compares the two.

Rewrapping rebuilds the lines it touches, with new breaks and new positions, so check the page after such an edit.

More questions about editing paragraphs in a PDF

Can I join two lines into one?

No. Words cannot move from one line to another, and a line holds no line break.

Can I add a sentence at the end of a paragraph?

Only if it fits on the last line. A new line is new text, which PDF Textfix does not add: see Can PDF Textfix add new text to a PDF?.

Can I change the line spacing or the font of a paragraph?

No. PDF Textfix changes no fonts or sizes and moves no lines.

What is text reflow?

Rewrapping text into new lines when the words or the width change, so that words move from the end of one line to the start of the next. A word processor does it as you type. In a PDF the lines were fixed when the file was made, which is why an edit that needs it belongs in the source document or in an editor that rebuilds the lines.