From Tracker Software PDF SDK
Creates a new bookmark and inserts it as a bookmark's sibling (before or after it on the same level).
HRESULT AddNewSibling([in] VARIANT_BOOL bBefore, [out, retval] IPXC_Bookmark** pSibling);
- [in] Choose whether the created sibling should be inserted before or after the bookmark.
- [out, retval] Pointer to IPXC_Bookmark containing the newly created sibling.
Returns S_OK if the operation was successful, or will return an error code if it fails.