Start with what you need to preserve
For a paper with figures, a form, or a document whose page references matter, the original PDF layout can be useful. For a novel or another mainly text-based book on a small screen, EPUB’s adjustable text can make it easier to settle into a comfortable reading size.
The choice is limited by the files you can obtain legitimately. Reader imports both formats; it does not convert one format into the other or remove document protection.
How the formats behave in Reader
| Question | EPUB | |
|---|---|---|
| Does the original page design stay in place? | Yes. The document controls the page typography and layout. | Text adapts to the reading view; source styling can affect the result. |
| Can I adjust the book’s text in Reader? | Reader does not re-typeset the PDF page. | Reading Settings includes EPUB text adjustments. |
| What does the reading theme change? | The controls and area surrounding the original page. | The reading view, including its text presentation. |
| Can I use passage actions? | When the PDF has usable selectable text. | When the passage contains selectable text. |
| Is an account needed for ordinary reading? | No ChatGPT account is needed. | No ChatGPT account is needed. |
When a PDF looks right but selection does not
A PDF can be a collection of scanned images. Looking like text does not necessarily mean it has a selectable text layer. Even when text is selectable, its extraction order may differ from the printed layout, especially in multi-column documents.
Reader does not currently advertise built-in OCR. If passage selection is important, use a document with a suitable text layer or ask the publisher for an accessible EPUB. Do not assume an AI model can read text that the app cannot select.
Keep the useful source
Try a few pages before committing to a long reading session. Check small text, diagrams, notes, and any passage you want to translate. Keep your original file outside the app so you can choose a different version later.
Next, import your PDF or EPUB or learn how to use ChatGPT with selected text.