Free PDF text highlighter: how to permanently highlight all occurences of a word at once?

Question

Objective:

1. I need to speed read hundreds or academic articles when doing Systematic Literature Reviews;
2. the main idea is to do skimming in order to find just the information that I need to exclude/include/tabulate/summarize the articles, but not read all of them from beginning to end;
3. this is easier to do when the keywords are already highlighted (as in highlighter pen on printed paper) prior to reading: I know visually where I'm more prone to find the information that I need and I focus on these sentences only;
4. however, manually highlighting the keywords each-by-each is very time-consuming, and error-prone.

How I do it today:

1. I open one PDF article on Sumatra PDF Reader v3.5.15481 64-bit Pre-release;
2. I use CTRL+F to find one keyword, and press A to highlight it on yellow (or S to strike it out on black);
3. I press F3 to jump to the next occurrence of the same keyword, and repeat steps 2 and 3 until all occurrences of that keyword have been highlighted;
4. having highlighted all occurrences of one keyword on one PDF, I close it with CTRL+W, and select "Save on an existing PDF", overwriting it. Now the PDF is pemanently hightlighted and ready for skimming;
5. I open the next PDF article and do the same search and highlighting for each occurrence.

It is already a time-consuming and error-prone process when you have only one keyword to highlight and hundreds of PDF files to skim through, but it gets worse when you, like me, have a dozen different keywords to highlight on each of the hundred PDFs...

What I am looking for:

A free program that permanently highlight all occurrences of one keyword on one PDF file at once, letting to me just the work of saving it.

Is there any that can do this? Which one? How?

What I am not looking for:

• a way to highlight the keywords only while the PDF file is open on my screen -- I need the highlight to be not just an exhibition imposed on the file by the program, but a permanent edit of the file, just like I do currently;
• a way to highlight a batch of keywords at once on many PDFs at once -- there is already a question for that, and there is no answer at all, so this probably isn't feasible, so I'm lowering my expectation.

Answer 1

You can use PyMuPDF python library

https://pypi.org/project/PyMuPDF/

Example program:

import fitz

highlights = ["word1", "word2"]

doc = fitz.open("input.pdf")
for page in doc:
    for text in highlights:
        quads = page.search_for(text, quads=True)
        for quad in quads:
            annot = page.add_highlight_annot(quad)
            annot.update()

doc.save("output.pdf")

guide for installation

Answer 2

Adobe Acrobat

Adobe Acrobat is a useful PDF software that you need to install on your device. But first is this software compatible with your computer or phone. Adobe Acrobat is a cross-platform that supports Windows, Mac, Linux, Android phones, and Windows phones. This makes it possible to view and manage PDF files on your phone as well as PC. To be precise it supports Windows: 10, 8, 7, XP, and Server. For Mac, it supports macOS X 10.6, 10,7, 10,8, 10,9, 10,10.

Homepage: https://acrobat.adobe.com/us/en/

Foxit PDF Editor

PDF Editor provides a powerful solution for business professionals to work securely with PDF documents and forms. It provides a full featured platform to view, create, edit, collaborate, share, secure, organize, export, OCR, and sign PDF.

PDF Editor Pro is geared towards power users who require advanced editing and security capabilities.

Homepage: https://www.foxit.com