To scroll page by page, you have to enable UIScrollView paging: 

in recent versions, you have simply to set g_paging_enabled = true in APP_INIT().

Paging is enabled only for viewMode 3 and 4.

For older version, follow this guide:

in PDFView.m, vopen() method, you have to set self.pagingEnabled = YES;.

To manage the zoom, you have to set self.pagingEnabled = NO; in scrollViewDidZoom() method, then add this code ad the end of scrollViewDidEndZooming() method:

if (self.zoomScale <= 1)

{

   self.pagingEnabled = YES;

   [self vGoto:m_cur_page]; <— this is optional, but you should manage the page position

}