Convert PDF Documents to Image Documents  

// Get the path of the PDF file.
NSString *pdfPath = @"...";
// Get the path to the ZIP file.
NSString *outputPath = @"...";

CPDFConvertImgOptions *options = [[[CPDFConvertImgOptions alloc] init] autorelease];
[options setType:CPDFConvertImgTypeJPEG];
//Image DPI
[imgOptions setImageDpi:200];

CPDFConverterImg *converter = [[[CPDFConverterImg alloc] initWithURL:[NSURL fileURLWithPath:pdfPath] password:nil] autorelease];
[converter convertToFilePath:outputPath pageIndexs:nil options:options];