Changing a word in a PDF is easy. Changing it so nobody can tell it was changed is the hard part. The usual giveaway is the font: the new word comes out in Arial or Helvetica while the rest of the line is in something else, a point bigger or a hair lower.
This guide explains where the font goes wrong and how to keep it.
Where the font in a PDF comes from
A PDF can carry its fonts inside the file. When it does, the file usually holds only a subset: the letters the document happened to use, and nothing else. If the original says "Invoice 2041" and you want "Invoice 2047", the 7 may simply not be in the file.
That is why so many editors give up and switch to a default font. They can see the name of the original typeface, but they cannot draw a letter that was never stored.
Some PDFs do not carry their fonts at all and rely on the reader's computer to have them. Then the editor has to find the same face, or one close enough, by itself.
What a good match needs
To look untouched, the new text has to agree with the old on:
- Typeface: the same family, or one with the same letter shapes and widths.
- Weight and style: bold stays bold, italic stays italic.
- Size: the same point size, not the nearest round number.
- Position: the same baseline, so the new words sit on the line rather than float above it.
- Spacing: the same gaps between words. A justified line has wider gaps than a ragged one.
- Colour: the same ink, which is often a very dark grey rather than pure black.
Miss any one of these and the eye catches it, even if the reader cannot say why.
How to do it in PencoPDF
The PDF text editor works line by line:
- Open Edit PDF text and choose your file.
- Click the line you want to change. Click again to put the cursor in it.
- Retype the words and click away.
The new words are set in the page's own font when the letters are in the file. When they are not, PencoPDF picks the closest face it has by name and by the width of the letters, so line lengths stay the same. It keeps the size, the weight, the baseline, the colour and the word spacing of the line you edited, and the old letters are removed from the file rather than covered over.
When the match cannot be perfect
- Unusual display fonts. A logo face or a decorative script may have no close match. Short changes still blend in, but a whole new sentence may not.
- Letters that were never in the file. A new character (an accented letter, a symbol) has to come from a similar font. At reading size this rarely shows. Zoomed in on a screen it can.
- Text that is a picture. If you cannot select the words at all, the page is probably a scan. Use the scanned PDF editor instead: it reads the letters first. See how to edit a scanned PDF.
Things that make the font go wrong elsewhere
- Adding a text box instead of editing the text. A text box is a new object with its own default font. It will not match unless you set it by hand, and the old words are still underneath.
- Round-tripping through Word. Converting the PDF to Word and back changes every font Word does not have, not just the line you edited.
- Copying and pasting. Pasted text arrives in the editor's default style.
If the edited line still looks off, why edited PDF text looks wrong goes through each cause and what to do about it.