A PDF document can consist of a variety of content types, one of them being plain text. PDF Viewer allows you to extract text from pages or from annotations in the document and to share the extracted text with other apps.
There are two different ways to share text:
Select text on a page by long-pressing it. You can change the selection by dragging the selection handles at the front and end of your selection. Once the text you would like to share is selected, tap the "Share" icon in the toolbar and select an app to share with.
Select a note annotation or freetext annotation. Annotations of these two types are the primary way of adding text to a PDF document. Once a note annotation or freetext annotation is selected, tap the "Share" icon in the toolbar and select an app to share with.
If you instead want to share an entire page (including all annotations, images, etc.) have a look at our page sharing article.