How to add blank pages while concatenating several PDFs using PdfSmartCopy

I'm trying to concatenate a huge number of PDF files to create a print-ready file, so that I don't have to print them one by one. The print-ready file I want needs to be duplex, so for the documents I have which are only 1 page, I need to add a blank page for the "back" of the document, otherwise the following document is messed up.

Is there any way to add blank pages while concatenating files using PdfSmartCopy? I know PdfWriter can easily add blank pages, but it isn't made for merging a large number of files, which is why I'm not using it. I've read the answer to the question "How to add blank pages in exist PDF in java?" However, in this case I can't use PdfStamper either because I require a small file size and it seems PdfSmartCopy is the only viable option for that, unless I have missed something.

Posted on StackOverflow on Jan 30, 2014

In my answer to the question you refer to, I explained how to insert a blank page into an existing PDF using PdfStamper. This doesn't help you, because you're using PdfSmartCopy, which is an extension of PdfCopy. When using PdfCopy (or its subclass PdfSmartCopy), you can use the addPage() method like this:

copy.addPage(PageSize.A4, 0);

In this case, a page with size A4 will be added. In your case, you'd want to make sure that the blank page has the same dimensions as the other pages in your documents, so you'll do something like this:

copy.addPage(reader.getPageSize(1), reader.getPageRotation(1));

The Rectangle value will now correspond with the size of the first page in the reader; the int value will correspond with the rotation of the first page of your existing document.

Click this link if you want to see how to answer this question in iText 7.