I have the same problem too.
I want to remove the highlight annotation when i tap it.
I think it is not working because of Page_getAnnotFromPoint( pdfPage, x, y ) might have a bug.
( when I use Page_getAnnot(index), it works well.)
- (void)OnSingleTapped:(float)x :(float)y
{
struct PDFV_POS pos;
[m_view vGetPos:&pos];
PDFVPage *vPage = [m_view vGetPage:pos.pageno];
PDF_PAGE pdfPage = vPage.GetPage;
NSLog(@"pdfPage:%@", [NSValue valueWithBytes:&pdfPage objCType:@encode(PDF_PAGE)]);
// !!!: I can get pointer like "0x7b4cba0".
PDF_ANNOT annot = Page_getAnnotFromPoint( pdfPage, x, y );
NSLog(@"annot:%@", [NSValue valueWithBytes:&annot objCType:@encode(PDF_ANNOT)];
// !!!: I cannot get pointer like "00000000"
Page_removeAnnot(pdfPage, annot);
annot = NULL;
[m_view vRenderPage:pos.pageno];
/ *** /
}