How to draw a PDF to a CGContext with a higher resolution?

I wrote a view to render a PDF Page:

-(UIPDFRenderView*) initWithFrame:(CGRect)frame withDocument:(CGPDFDocumentRef*)document withPageNumber:(int)pageNumber
{        
    if (self) 
    开发者_开发技巧{
        page = CGPDFDocumentGetPage (*document, pageNumber);

        pageRect = CGPDFPageGetBoxRect(page, kCGPDFMediaBox);
        pdfScale = (CGRectGetWidth(frame)/pageRect.size.width);

        rect = frame;
        self = [super initWithFrame:CGRectMake(CGRectGetMinX(frame),
                                               CGRectGetMinY(frame),
                                               CGRectGetWidth(frame), 
                                               CGRectGetHeight(pageRect) * pdfScale)];
    }
    return  self;
}


-(void) drawRect:(CGRect)rect
{
    [self displayPDFPageWithContext:UIGraphicsGetCurrentContext()];    
}

-(void) displayPDFPageWithContext:(CGContextRef)context
{
    CGContextSetRGBFillColor(context, 1.0,1.0,1.0,1.0);
    CGContextFillRect(context, self.bounds);

    CGContextSaveGState(context);
    CGContextTranslateCTM(context, 0.0, self.bounds.size.height);
    CGContextScaleCTM(context, pdfScale,-1*pdfScale);

    CGContextDrawPDFPage (context, page);
}

I use one of that view for every page of a pdf document and add them to a acrollview. The problem is if i zoom in, the page is pixelig. No surprise because i am using the screen context to render the pdf. Is there any posibility to render that pdf with the double resolution to enable zoomin to a factor of 2?

---

Okay i got the solution, i render it in original size and initiate the scollview with a low scale that the width of the pdf fits with the width of the scrollview. With that methode i can zoom till original size (scale of 1).