This article shows how to set the page corner radius:

Modify both DrawBmp methods, in PDFVCanvas adding

    CGPathRef clippath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(x/m_scale, y/m_scale, w/m_scale, h/m_scale) cornerRadius:10.0].CGPath;

    CGContextAddPath(m_ctx, clippath);

    CGContextClip(m_ctx);

after CGContextSaveGState(m_ctx);