How to use the highlight text in pdf by search
- Choose a PDF, up to 25 MB and 500 pages. The page reads its text layer.
- Type the words or phrases to highlight, one per line or separated by semicolons.
- Choose a color and strength, and set whether capital letters must match exactly and whether only whole words count.
- Check the table of matches by term and page, then download the highlighted PDF.
Formula
The text of each page is read with its position, one piece at a time, from the PDF
A term matches where its text occurs in the page text. Longer terms are matched first, so "red apple" takes its words before "red" does.
Each match gets a box along the text, found from the start and end of the match inside the pieces it spans
The boxes are drawn with the multiply blend, so the text under them stays dark and readable
The edges of a box inside a long piece of text are placed from letter widths and the width the PDF reports, so on a long line in an unusual font they can be off by a little.
Searching for fox in two pages
Page 1 reads "The quick brown fox jumps over the lazy dog." and "Fox and fox. The red apple is red." Page 2 reads "Fox in a box. foxes". Searching for fox without caring about capital letters finds 5 matches: 3 on page 1 and 2 on page 2. Requiring exact capital letters finds 3, and whole words only finds 4, because "foxes" is not a whole word.
Searching for both "red apple" and "red" finds 2 matches on page 1, not 3, since "red apple" takes its first word. Searching for "fox" and "dog" together finds 6. The box for "brown fox" begins at the start of the word brown and has the width of that phrase in Helvetica, and the output has one extra drawn box for each match while all the original text is unchanged.
Highlighting for review
Highlighting every occurrence of a name, a term or a number helps when you check a contract, a report or a paper. The summary table tells you how many matches each term has and on which pages, so you can tell at a glance if a term never appears. The highlights are drawn on the page and not added as editable annotations, which keeps them showing in every viewer.
To search a PDF and see each match in context, use the PDF text search. To get all of the text out of a PDF, use PDF to text, and to compare two PDFs see compare PDF.
Scans and split text
A PDF that is a scan or a photo has no text layer, so there is nothing to search, and the page says so. Text on a line is matched across the pieces the PDF splits it into, but a term broken by a line end or placed in separate columns is not matched. Letters with accents match only the same letters, and hyphenated words split across lines are not joined.
Your original file is not changed. Add notes next to the highlights with the add text to PDF tool. Nothing is uploaded.
Assumptions and limits
- The PDF has a text layer. Scans and pictures of text cannot be searched.
- A term must lie on a single line of text. Terms broken across lines are not matched.
- Matching is by characters and does not know about plurals or word forms.
- The page allows up to 50 search terms of up to 200 characters each.
Frequently asked questions
How do I highlight text in a PDF?
Choose the PDF, type the words to find and download the file with a colored box over every match.
Does it work on a scanned PDF?
No. A scan is a picture, so there is no text to find. Use a text recognition program first.
Can I highlight several words at once?
Yes. Put one per line or separate them with semicolons, and each gets its count in the table.
Will the text stay readable?
Yes. The boxes are see-through and use a multiply blend, so the text shows through the color.