# Why can't I highlight in PDF lecture notes for my exam? **URL:** \ **Category:** Annotations & Notes\ **Tags:** reading\ **Created:** [October 29, 2026, 3:02pm UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49 "2026-10-29T15:02:29Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![john\_turner](https://pdfbookslib.com/discussions/letter_avatar_proxy/v4/letter/j/87869e/32.png) [@john\_turner](https://pdfbookslib.com/discussions/u/john_turner)\ **Post date:** [October 29, 2026, 3:02pm UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/1 "2026-10-29T15:02:29Z")
My exam is next week and I’m going through the lecture slides my professor uploaded as PDFs, but the highlight tool just won’t do anything on them. I tried on my laptop and my phone, same problem. Is it because they’re scanned or something? ---
**Author:** ![reid21](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/reid21/32/22_2.png) [@reid21](https://pdfbookslib.com/discussions/u/reid21)\ **Post date:** [October 29, 2026, 3:02pm UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/2 "2026-10-29T15:02:31Z")
Honestly, if you can’t select the text either, they’re probably scanned page images, so the highlighter has nothing to grab onto. Quick fix is running OCR: open the PDF in Word or upload it to Google Docs, both do a decent job adding a text layer. Then highlighting works. To be fair I hit this with old scanned drawing sets all the time. ---
**Author:** ![finlay.wilson](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/finlay.wilson/32/23_2.png) [@finlay.wilson](https://pdfbookslib.com/discussions/u/finlay.wilson)\ **Post date:** [October 29, 2026, 10:36pm UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/3 "2026-10-29T22:36:52Z")
I had this exact problem with scanned documents at work. If the slides are saved as flat images, your device cannot recognise the words to highlight them. What worked for me was running the file through the OCR tool on PDFcap. That turns the picture of the text into real, selectable text you can highlight. ---
**Author:** ![emily.7](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/emily.7/32/26_2.png) [@emily.7](https://pdfbookslib.com/discussions/u/emily.7)\ **Post date:** [October 30, 2026, 2:21am UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/4 "2026-10-30T02:21:57Z")
@reid21 the Google Docs route is what I’d try too, it adds the text layer for free. Formatting drifts a bit on my old laptop, but highlighting works. Not sure if it’s the same on Mac. ---
**Author:** ![code\_pal](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/code_pal/32/27_2.png) [@code\_pal](https://pdfbookslib.com/discussions/u/code_pal)\ **Post date:** [October 30, 2026, 4:21am UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/5 "2026-10-30T04:21:54Z")
@emily.7 Google Docs works on a Mac through the browser too, though the slide layout can shift. I’d keep the original untouched, run OCR on a copy, then use that copy for highlighting and the original for checking diagrams. ---
**Author:** ![sarcastic\_sea](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/sarcastic_sea/32/33_2.png) [@sarcastic\_sea](https://pdfbookslib.com/discussions/u/sarcastic_sea)\ **Post date:** [October 30, 2026, 9:06am UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/6 "2026-10-30T09:06:53Z")
If they are scanned, they are just pictures of text, which is why your highlighter has nothing to grab. I learned this the hard way when dealing with supplier ingredient lists. Try opening the file in Google Docs or Word to see if it will recognise and convert the text for you. Do not waste hours trying to force a basic reader to highlight an image. ---
**Author:** ![SneakySteel](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/sneakysteel/32/25_2.png) [@SneakySteel](https://pdfbookslib.com/discussions/u/SneakySteel)\ **Post date:** [October 30, 2026, 11:51am UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/7 "2026-10-30T11:51:45Z")
Had the same thing last month with a scanned handout. If the text won’t highlight on both laptop and phone, it’s almost certainly an image based PDF with no real text layer, so highlighting tools can’t grab anything to select. You’d need to run OCR to add a text layer first. On Kindle specifically, highlighting scanned PDFs basically never works at all. ---
**Author:** ![evelyn2008](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/evelyn2008/32/34_2.png) [@evelyn2008](https://pdfbookslib.com/discussions/u/evelyn2008)\ **Post date:** [October 30, 2026, 9:06pm UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/8 "2026-10-30T21:06:46Z")
If it fails on both devices, the slides are probably scans or the PDF has restrictions. I usually test by trying to select one word: if there is no text cursor, I run OCR first in Acrobat or PDF-XChange, then save a copy for highlighting. For exam prep, I also keep the original untouched and mark the OCR copy, since OCR can misread small symbols. ---
**Author:** ![wallabies](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/wallabies/32/35_2.png) [@wallabies](https://pdfbookslib.com/discussions/u/wallabies)\ **Post date:** [October 31, 2026, 11:06am UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/9 "2026-10-31T11:06:44Z")
Sounds like your slides are scanned images, not real text, so the highlight tool has nothing to grab onto. Try running them through OCR first, I learned this the hard way with old course packs. On Windows you can do it right in Adobe with Recognize Text, otherwise scan-tailor or online tools work too. ---
**Author:** ![user.871065](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/user.871065/32/30_2.png) [@user.871065](https://pdfbookslib.com/discussions/u/user.871065)\ **Post date:** [October 31, 2026, 10:51pm UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/10 "2026-10-31T22:51:48Z")
@evelyn2008 The select-a-word test is what I do at work too, it saves so much guessing. At my desk I drop the file into Word first since it adds a text layer without touching the original, then I highlight a copy and keep the clean scan for the diagrams. ---
**Author:** ![isaacd99](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/isaacd99/32/36_2.png) [@isaacd99](https://pdfbookslib.com/discussions/u/isaacd99)\ **Post date:** [November 1, 2026, 2:36pm UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/11 "2026-11-01T14:36:55Z")
yeah if theyre scanned its just pictures of the slides so highlight wont work. try ocr to add a text layer, i use that on old lease scans sometimes. not sure if its the same on your phone though. ---
**Author:** ![new\_user.71287](https://pdfbookslib.com/discussions/user_avatar/pdfbookslib.com/new_user.71287/32/37_2.png) [@new\_user.71287](https://pdfbookslib.com/discussions/u/new_user.71287)\ **Post date:** [November 2, 2026, 10:21pm UTC](https://pdfbookslib.com/discussions/t/why-cant-i-highlight-in-pdf-lecture-notes-for-my-exam/49/12 "2026-11-02T22:21:47Z")
Yeah, that sounds like scanned pages. Quick test: drag your cursor over some text. If nothing gets selected, the pages are just images and the highlighter has nothing to grab onto. The fix is running OCR on the file, Adobe Acrobat has it built in under the scan and ocr tools, or free options like OCRmyPDF. Honestly I did this with my old cert notes and highlighting worked right after.