If you have a version of a document that has bookmarks and want to copy them over, a much simpler way is to use PDF-XChange Viewer (I used v2.5.211). Open the PDF that has the bookmarks (the source PDF), select all the bookmarks in the bookmarks pane, copy them using Ctrl+C, open the PDF that doesn't have the bookmarks (the target PDF), and paste them (Ctrl+V) in that PDF's bookmarks pane. PDF-Xchange Viewer preserves bookmark properties as they were from the source PDF (including any bold / italic formatting on the bookmark text). If for some reason some of the sections of the target PDF are lower or higher due to revisions made to the document, you can click the bookmark needing correction, scroll to where on the page you'd like the bookmark to open to, right-click the bookmark again and click "Set Destination". Repeat this last part as needed for any offending bookmark. Save the target PDF when finished.
This worked great for me, was quite intuitive, and I was done in a few minutes. In my particular scenario, a co-worker had produced a very long document using Word for Mac which didn't have bookmarks. Due to the length of the document, I wanted bookmarks corresponding to the document's outline. I could get Word for Windows to save the document as a PDF with bookmarks, but some formatting differences between Word for Windows and Word for Mac threw off the page count quite off (in particular, there were differences in white space around footers, and differences in the spacing between figures and the caption). I was able to play around with the headers & footers and figure sizes to get the pagination correct in Word for Windows, then saved to PDF w/ bookmarks. Unfortunately, there still were some differences in the formatting such that I wished to just apply the bookmarks to the original PDF, and that's when I figured out the solution above.