For complete examples and data files, please go to https://github.com/aspose-pdf/Aspose.Pdf-for-C
// Open first document
auto doc1 = MakeObject<Document>(L"..\\Data\\Pages\\Concat1.pdf");
// Open second document
auto doc2 = MakeObject<Document>(L"..\\Data\\Pages\\Concat2.pdf");
// Add pages of second document to the first
doc1->get_Pages()->Add(doc2->get_Pages());
// Save concatenated output file
doc1->Save(L"..\\Data\\Pages\\ConcatenatePdfFiles_out.pdf");