Use the Typewriter tool in Edit > Modify to add text at any suitable place on a PDF page. The Typewriter tool enters text directly at the cursor position. When the PDF is saved, the entered texts become an integral part of the PDF page, unlike texts entered as annotations, e.g. with the Text Box tool.
Text can also be pasted onto a Typewriter tool cursor. That means text blocks can be copied from Normal or Searchable PDF files and pasted into other PDF pages in the same or different documents. Document Assembly view is useful for such operations.
As text is entered or pasted, in-place spell checking will be performed if it is enabled under File > Options > Spell Check. Spell checking cannot be run explicitly on typewriter tool text.
Until the PDF is saved, you can move typewriter texts; select the Typewriter tool again and click in the text. A surrounding box appears that can be dragged to a new location. Double click to edit the text.
To change text properties on the selected text, use the TypeWriter Format Ribbon, which is automatically displayed when using the TypeWriter tool.
Larger changes to real PDF content can be made using Advanced Edit mode.
You can use the Edit Text tool in the Edit ribbon to modify typewriter texts after they have been saved. This tool allows editing of existing PDF text.
For more detail on the differences between typewriter texts and box texts, see Text Box.