How to Print a PDF File Using Cocoa

Mac OS X is well known for its great support for PDF files. You can create a PDF file from anything you can print. I thought that using Apple’s PDFKit framework would make it easy to program a way to print an existing PDF file. That turned out not to be the case.

Sending a file to a printer using the lp command is easy. However, this approach does not work for PDF files formatted for landscape printing. You can specify landscape orientation, but I wanted a way to detect the orientation automatically.

PDFKit has a PDFView object that has a printWithInfo:autoRotate: method. However, adding a PDFDocument to a PDFView and telling it to print doesn’t work. I eventually stumbled onto the fact that PDFDocumenthas a secret method that makes printing easy. So here is the code:

#import <Quartz/Quartz.h>

- (void)printPDF:(NSURL *)fileURL {

    // Create the print settings.
    NSPrintInfo *printInfo = [NSPrintInfo sharedPrintInfo];
    [printInfo setTopMargin:0.0];
    [printInfo setBottomMargin:0.0];
    [printInfo setLeftMargin:0.0];
    [printInfo setRightMargin:0.0];
    [printInfo setHorizontalPagination:NSFitPagination];
    [printInfo setVerticalPagination:NSFitPagination];

    // Create the document reference.
    PDFDocument *pdfDocument = [[[PDFDocument alloc] initWithURL:fileURL] autorelease];

    // Invoke private method.
    // NOTE: Use NSInvocation because one argument is a BOOL type. Alternately, you could declare the method in a category and just call it.
    BOOL autoRotate = YES;
    NSMethodSignature *signature = [PDFDocument instanceMethodSignatureForSelector:@selector(getPrintOperationForPrintInfo:autoRotate:)];
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
    [invocation setSelector:@selector(getPrintOperationForPrintInfo:autoRotate:)];
    [invocation setArgument:&printInfo atIndex:2];
    [invocation setArgument:&autoRotate atIndex:3];
    [invocation invokeWithTarget:pdfDocument];

    // Grab the returned print operation.
    NSPrintOperation *op = nil;
    [invocation getReturnValue:&op];

    // Run the print operation without showing any dialogs.
    [op setShowsPrintPanel:NO];
    [op setShowsProgressPanel:NO];
    [op runOperation];
}

I consider this code to be in the public domain. Please feel free to copy and paste. And let me know if you find any problems or have suggestions.

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