5.4. How to annotate PDF files

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:

1. Open a PDF document;
   
2. Tap Annotate on the top toolbar;
3. Select the Highlight , Underline  or Strikeout tool. You can select the color for each tool by tapping the color picker ;
   
   
   
   
4. Select a text to annotate it;
5. To remove the annotation, please long tap the text and select Clear in a pop-up menu. Alternatively, you can tap on the toolbar. If you need to redo your edits, tap and hold and select Redo.

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:

1. Select Annotate on the top toolbar;
   
2. Choose the needed annotation tool and tap its color;
3. Tap the color wheel on the right;
   
4. Tap the color preset you'd like to modify and pick up the color you wish. You can repeat these actions for each of five presets;
   
5. To return to the default color pallet, tap Restore;
   
6. You can also pick colors from the currently opened document. For this, please tap the eyedropper tool;
   
7. Drag the eyedropper over the color you want to use. Once you've picked the desired color, tap Done. This color will appear in your pallet.

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.