Merge pdf - Empty page

Question

Guys,
I am trying to merge some pdf files into one file. This is my code
- (BOOL) concateFiles:(NSArray *) filePaths {
    PDFDocument * outputDocument = [[PDFDocument alloc] init];
    NSUInteger pageIndex = 0;
    for (id file in filePaths) {
        PDFDocument * inputDocument = [[PDFDocument alloc] initWithURL: [NSURL fileURLWithPath:file]];
        for (NSUInteger page = 0; page < [inputDocument pageCount]; page ++ ) {
            [outputDocument insertPage: [inputDocument pageAtIndex:page] atIndex:pageIndex++ ];
    //BOOL done = [outputDocument writeToFile: @"/Users/bubuzzz/test.pdf"]; // does not work
    NSError *error = nil;
    NSString * filePath=@"/Users/bubuzzz/test.pdf";
    NSData * data = [outputDocument dataRepresentation];
    BOOL done = [data writeToFile:filePath options:NSDataWritingAtomic error:&error]; // does not work either
    NSLog(@"Write returned error: %@", [error localizedDescription]);
    return done;
There is no error during run time. However, the created file only has empty page, though the number of page is correct. The only thing I find out is using CGPDFContextClose to close the context to make it work fine, since it is stated in the document
After closing the context, all pending data is written to the context destination, and the PDF file is completed. No additional data can be written to the destination context after the PDF document is closed.
However, I have no idea how to integrate the CGPDFContextClose into my code. Any suggestion, please?

Answer 1

Just change the above code to do a page by page vopy like yours and it works
#import <Foundation/Foundation.h>
#import <Quartz/Quartz.h>
int main(int argc, const char * argv[])
    @autoreleasepool {
        // insert code here...
        PDFDocument * inputDocument;
        PDFDocument * outputDocument = [[PDFDocument alloc] init];
        NSUInteger pageIndex = 0;
        NSURL * pdfFile = [NSURL  fileURLWithPath:@"/Users/frank/Desktop/Hold/TX-SR304_En_0124.pdf"];
        // open old PDF
        if ((inputDocument = [[PDFDocument alloc] initWithURL: pdfFile]) == NULL) {
            NSLog(@"error opening");
            return 0;
        // copy old PDF to new PDF
        //outputDocument = inputDocument;
        for (NSUInteger page = 0; page < [inputDocument pageCount]; page ++ ) {
            [outputDocument insertPage: [inputDocument pageAtIndex:page] atIndex:pageIndex++ ];
        //write new PDF
        [outputDocument writeToFile:@"/Users/frank/Desktop/Hold/testCard.PDF"];
    return 0;
When this is done testCard.PDF has the contents of the input file.