PdfDocument's copyPagesTo method or PdfCanvas's copyAsFormXObject to copy content from PDF to PDF - pdf

Question

I followed the guide at this URL: http://developers.itextpdf.com/content/itext-7-jump-start-tutorial/chapter-6-reusing-existing-pdf-documents
Following that guide, I had a problem where some content from the PDF was not copied into the destination PDF when using copyAsFormXObject (which I submitted a support ticket for). An alternative I found in the meantime was that I could use the PdfDocument's copyPagesTo method and simply open the page that was copied with getPage on the destination PDF. From that, I can create a PdfCanvas from the existing page and do our transformations (such as scaling) on the object.
This seems to work exactly as the code in the aforementioned guide with the exception that the PDFs I found where content wasn't copied, the content now appears to be copied.
Are there any drawbacks to using the copyPagesTo method to copy the content as opposed to what the guide suggests (copyAsFormXObject)? Performance, memory, or extraneous non-visible content, etc.?
Code that exhibits this problem:
PdfDocument pdf = new PdfDocument(new PdfWriter(dest));
PdfDocument origPdf = new PdfDocument(new PdfReader(src));
PdfPage origPage = origPdf.getPage(1);
PdfPage page = pdf.addNewPage();
PdfCanvas canvas = new PdfCanvas(page);
PdfFormXObject pageCopy = origPage.copyAsFormXObject(pdf);
canvas.addXObject(pageCopy, 0, 0);
pdf.close();
origPdf.close();
Code that does not:
PdfDocument pdf = new PdfDocument(new PdfWriter(dest));
PdfDocument origPdf = new PdfDocument(new PdfReader(src));
origPdf.copyPagesTo(1,2,pdf);
pdf.close();
origPdf.close();

Answer 1

I've provided code and answers for the specific problem on your support ticket.
As for the difference between copyToPages() and copyAsFormXObject() for copying pages:
copyToPages() is a high level method that copies over the entire page, maintaining all structure and adding any applicable resources to the new document.
With copyAsFormXObject(), you first need to transform the page to an XObject, essentially turning it into an appearance stream. If this page needs additional settings or resources to be displayed correctly, such as a different page size or fonts that were not stored on the page itself, they need to be manually set or added. XObject are always added at absolute positions, so this needs to be specified too.
While copying using low-level methods such as XObjects grants a lot more control over what the result can look like, they come with their own dangers and pitfalls. For ubiquitous tasks such as copying pages, it is better to use the high-level methods to avoid such possible problems.
EDIT:
We've decided that this behaviour is a bug and that 'copyAsFormXObject()' should include the used resources even if they're stored at the /Pages level. This will be fixed in a later release of iText