Documents introduces the powerful built-in PDF reader. The app allows you to highlight, underline and strike through PDF texts with different colors. This is a great way to work with a document and emphasize its key points.
Kindly note that you can use these types of annotations in text-searchable PDF files (i.e. PDFs with text layers); if you work with a scanned PDF file where text content is not searchable, you will need to OCR the file first or use Marker/Pen tools with the necessary opacity level to highlight or underline text.
How to apply these annotation to a PDF text:
Kindly note that when any annotation tool is active, use the two-finger scrolling to navigate the document.
Besides, in Documents, we have introduced a great number of annotation colors and let our users customize the color palette for their own needs.
How to customize annotation colors:
For free, you can not only annotate PDFs, but also add sticky notes and comments, draw with the Apple Pencil, paste shapes, and even fill out forms. For more information regarding the powerful built-in PDF reader, please refer to this article.