# Annotate, Highlight, or Index a Document

- Use the VAPIM_ENABLEINDEX message to enable index-only mode. This generates text buffer (`VAPINM_TEXTBUFFER`) notification messages with document viewing disabled.

- To specify the character set for the returned text buffer, use VAPIM_SETINDEXBUFCHARSET.

- To add and delete annotations, use the VAPIM_ANNOTATE message. The annotation is placed at a logical address.

- To add a highlight to a document, use the ``VAPIM_SETHILITE message.

- See the following messages and notification messages for more functionality related to annotating, highlighting, or indexing documents:

  - VAPIM_GETNEXTTEXTBUFFER

  - VAPIM_GETPAGEFROMLOGICAL

  - VAPIM_GETTEXT

  - VAPIM_GOTO_PAGE

  - VAPIM_POSITION

  - VAPIM_SETCURSOR

  - VAPIM_SHOWHITS

  - VAPINM_ANNOTATION_HIT

  - VAPINM_EXTENT

  - VAPINM_SELECTION

  - VAPINM_USERCLICK

  - The VAPIMWP_PRINT_ANNOTATIONS parameter of `VAPIM_PRINT`

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