OmniDocHow to Annotate a PDF on iPhone
Learn how to highlight, underline, and note a PDF on your iPhone, what to check first, and when a scanned file needs OCR on a computer.
You receive a contract, a research paper, or a class handout on your phone, and you want to highlight the key passages and leave a few notes. Phone screens make that harder than it should be, and it is not always clear which steps happen on the iPhone and which need a computer. This guide walks through how to annotate a PDF on iPhone from start to finish.
You will learn which markup tasks work directly on the phone, how to check whether a file will take highlights, and how to mark up the PDF step by step. You will also see where OmniDoc fits in. The OmniDoc website opens in a phone browser for uploading and translating documents, and the desktop client handles the PDF editing tasks that the phone's viewer does not.
How do you annotate a PDF on iPhone? The short answer
Highlights, underlines, and notes on a text PDF can be added in the file viewer on your iPhone. Scanned pages, signatures, and form fields are better handled on a computer with the OmniDoc desktop client. Use the table below to pick the right route.
| Your situation | What to do | Why |
|---|---|---|
| You need highlights, underlines, or notes on a text PDF | Open the file in your iPhone's PDF viewer and use its markup tools | Nothing is uploaded, and the file stays on your phone |
| The PDF is a scan and you cannot select any text | Run OCR in the OmniDoc desktop client, then mark up the copy | OCR adds selectable text, so highlights attach to real words |
| You need to sign or fill in a form | Use the sign and form tools in the desktop client, or send a sign request | These PDF editor features are listed for the desktop client |
| You want to read the PDF in another language | Upload it at omnidoc.top in your phone browser and choose bilingual output | Side-by-side pages give you the original and the translation to annotate |
Before you start
- Make a copy first. Mark up a duplicate, not the only copy you have. If a note lands in the wrong place, you still have a clean version to start over from.
- Test whether the text is selectable. Press and hold on a line of body text. If you can select words, highlights will attach to them. If nothing selects, the page is probably a scan, and you should use OCR first.
- Check that the file allows changes. Some PDFs are locked for viewing only. If the owner restricts editing, the viewer may not save your marks.
- Have spare space on your phone. Saved annotations add a little size to the file, and a full storage drive can stop the save.
- Confirm you may share the file before uploading. Uploading a PDF to a website sends its contents to that service. Only upload documents you are allowed to share, and read the site's privacy information before you send anything sensitive.
Annotating a PDF on your iPhone, step by step
- Get the PDF onto your phone. Save the email attachment or download the file from a link into your phone's file storage. Keeping it in one place makes it easier to find when you need it again.
- Open the PDF in the viewer. Tap the file. It should open in your phone's built-in PDF viewer or in the app you used to download it.
- Show the markup tools. Look for the pen-tip or markup icon in the viewer's toolbar. Tapping it reveals the annotation options.
- Pick a tool and a color. Choose highlight, underline, a text note, or a freehand pen. Pick a color that stands out against the page, such as yellow for highlights and a darker shade for notes.
- Mark the passages. Drag across text to highlight or underline it. To add a note, tap the spot you want, type your comment, and place it. You can also draw directly on the page.
- Save the changes. Close the markup tools and confirm that the viewer saves the file. If it asks whether to keep your changes, choose to keep them.
- Translate and annotate if needed. Open omnidoc.top in your phone browser, upload the PDF, and choose bilingual output. Download the result, then mark up the bilingual copy the same way. If the page does not load on your phone, use a computer for the upload.
If the PDF is scanned
A scanned PDF is a picture of each page, so text markup often fails. Open the file in the OmniDoc desktop client for Windows, macOS, or Linux, which you can download at download.omnidoc.top. Run OCR on the file, save the result, and copy it to your iPhone. Then follow the steps above on the new copy.
Check the result
Once you have saved the marked-up file, reopen it and check it before you rely on it.
| Check | How to see it | If it's wrong |
|---|---|---|
| Highlights sit on the right text | Reopen the file and tap a few highlights | Undo and redo the mark; if it drifts, the page may be a scan, so run OCR on a computer |
| Notes are readable | Zoom in on each note | Shorten the note or make the text larger in the viewer |
| The original is untouched | Compare with the copy you saved | Delete the marked file and start again from the copy |
| Translated pages keep their layout | Scroll through the bilingual output | Upload again, or check that the source PDF's text can be selected |
Machine translation and OCR can make mistakes, so check any important passage against the source before you act on it.
❓ FAQ
1. Can I annotate a scanned PDF on my iPhone without OCR?
Usually not for text markup. Highlights need selectable text, so run OCR on a computer with the OmniDoc desktop client first, then mark up the new copy on your phone.
2. Does the OmniDoc website let me mark up PDFs on my phone?
The website opens in a phone browser and is used for uploading and translating documents. The PDF editing tools, including signing, form filling, and redaction, are part of the desktop client. For highlights and notes on the phone itself, use the viewer on your iPhone.
3. Will my annotations stay in the file when I share it?
Saved annotations usually travel with the file, but the viewer on the other person's device may show them differently. Open the file on another device before you send it to confirm the marks appear.
4. Is it safe to upload a confidential PDF for translation?
Only upload files you are allowed to share, and read the site's privacy information first. For sensitive material, consider doing the markup on your phone and avoid uploading the document at all.
📝 Summary
To annotate a PDF on iPhone, highlight and note text PDFs in the phone's viewer, and run OCR on a computer when the file is a scan. Save a copy before you mark up, and check the saved result before you rely on it.
