Which PDFs work with ChatPDF? Text, scans, passwords, size
Updated 13 October 2026 · ChatPDF guides · 9 sources
AI can miss or misstate things. Summaries and answers from AI tools, ChatPDF included, can leave out important details or get them wrong. Check anything that matters against the document itself, especially legal, medical, financial and exam material.
- ChatPDF works with PDF files that contain selectable text. Scanned pages without a text layer are refused with a message that the PDF has no selectable text.
- Quick test: try to select a word or search for a word in the Preview app. If that works, the PDF has text. 1,2
- A scan can get a text layer through OCR first, for example with Preview’s Embed Text export option on iOS 27 or open-source tools such as OCRmyPDF. 3,4
- Plans limit pages per PDF and file size; a trial allows only a few short documents. Split long PDFs if needed.
ChatPDF reads the text inside a PDF, so the main question is whether your file actually contains text. Most PDFs exported from word processors, websites, slide software or publishers do. Scans and photos saved as PDF usually do not. This page covers how to check, how to fix the common problems and what the plan limits mean.
Quick compatibility table
| Kind of PDF | Works? | What to do |
|---|---|---|
| Exported from a word processor, slides, a website or a publisher | Yes | Add it as is. |
| Scanned with the iPhone scanner or a copier | Usually not | Add a text layer with OCR first. |
| Photos saved as a PDF | No | OCR it, or copy the text with Live Text. |
| Mixed: some typed pages, some scanned | Partly | Scanned pages contribute no text; OCR the whole file. |
| Password-protected | Use an unlocked copy | Ask the sender for an unprotected version, or keep one before locking. |
| Very long document or large file | Depends on your plan | Split it into parts. |
| Word, ePub, images and other formats | No | Export or save as PDF first. |
Check for selectable text
- Open the PDF in the Preview app (iOS 26 and later) 5.
- Touch and hold a word. If grab points appear and you can select and copy text, the page has a text layer 1.
- Or tap search and look for a word you can see on the page. If it is found, the text is there 2.
- Check a few pages, especially if the document was assembled from different sources.
If nothing can be selected, the page is a picture of text. That is what the app's "no selectable text" message means.
Fixing a scanned PDF
A scan needs OCR (optical character recognition), which estimates the text from the picture and adds an invisible text layer. ChatPDF needs that layer to exist before you add the file. The app itself does not include OCR. Options:
- Preview on iOS 27: Apple's guide lists an Embed Text option when exporting a PDF, which runs OCR on images to make the PDF searchable 3.
- OCRmyPDF on a computer: a free, open-source tool that adds text layers to scanned PDFs using the Tesseract OCR engine 4,6. It cannot recognize handwriting, and its documentation warns that reading order across columns can be wrong 4.
- Just a few lines? Use Live Text to copy text from an image instead 7.
OCR makes mistakes, especially with poor scans, small print, tables and unusual fonts, so check names and numbers afterward. Full steps are in how to get selectable text from a scanned PDF and how to scan documents to PDF.
Password-protected PDFs
Some PDFs need a password to open. We recommend adding an unlocked copy instead. If you are locking a PDF yourself in Preview, Apple suggests making a duplicate first if you want a copy that is not password-protected 8. If someone sent you a protected file, ask them for an unprotected version you are allowed to share, and think about whether a document that sensitive should go to any AI tool (see privacy of AI PDF tools).
Page and file size limits
Each plan limits how many pages a PDF can have and how large the file can be; larger plans allow longer documents. A free trial, where offered, allows only a few short documents. Check the app for the limits of your plan. If a document is too long:
- Make a copy of the PDF so the original stays intact.
- In Preview, show the page thumbnails and delete the pages you do not need, for example to keep one chapter 9.
- Repeat with another copy for the next part, then add each part as its own document.
Splitting by chapter often gives better answers anyway, because questions are matched against a smaller, more focused set of passages. See how to summarize a long PDF.
Other things worth knowing
- Layout-heavy files such as multi-column papers, forms and spreadsheets saved as PDF can lose structure when the text is extracted; tables in particular can scramble. See tables and numbers.
- Charts and diagrams contribute only their caption and labels, not the values drawn in them.
- Other languages are fine as long as the text is selectable. Answers come in the language of your question.
- Files outside Files must be saved to the Files app first; see getting started with ChatPDF.
Common questions
Why does ChatPDF say my PDF has no selectable text?
The file is a scan or photo without a text layer, so there is no text to read. Run OCR on it first, for example with Preview’s Embed Text export on iOS 27 or OCRmyPDF, then add the new file. 3,4
Can I add handwritten notes?
Only if the PDF contains real text. Common free OCR tools do not recognize handwriting, so handwritten pages usually stay unreadable. 4
How many pages can a PDF have?
It depends on your plan; larger plans allow longer documents, and a trial allows only a few short ones. Check the app for current limits, and split long PDFs by chapter if needed. 9
Sources and further reading
- Apple Support. Annotate a PDF or image in Preview on iPhone (iPhone User Guide). support.apple.com
- Apple Support. Open and view PDFs and images in Preview on iPhone (iPhone User Guide). support.apple.com
- Apple Support. Export or compress PDFs and images in Preview on iPhone (iPhone User Guide, iOS 27). support.apple.com
- OCRmyPDF documentation. Introduction. ocrmypdf.readthedocs.io
- Apple Support. Get started with Preview on iPhone (iPhone User Guide). support.apple.com
- Tesseract OCR. Tesseract User Manual (tessdoc). tesseract-ocr.github.io
- Apple Support. Interact with text in an image in Preview on iPhone (iPhone User Guide). support.apple.com
- Apple Support. Lock PDFs in Preview on iPhone (iPhone User Guide). support.apple.com
- Apple Support. Add, delete, rotate, move, or crop PDF pages in Preview on iPhone (iPhone User Guide). support.apple.com