Background Object Outlines on "Print Booklet" but not on "Export"

Question

I am using Adobe CS6 and have been using the "Export" function within InDesign for many years. I am tired of creating brochures in "Printer's Spreads":

[Blank Page] [8,1] [2,7] [6,3] [4,5]

I want to create the brochures in "Designer's Spreads":

[Page 1] [2,3] [4,5] [6,7] [8]

I know InDesign has an option "Print Booklet" that lets you create in "Designer's Spreads" and export the PDF in "Printer's Spreads".

The Problem

Whenever I export using "Print Booklet", I always get these thin outlines of background objects on my PDFs. I do not get these when I do a standard "Export" which is what I have been using the past few years.

I've verified as best I can that I am using the same options and Adobe PDF Presets when exporting PDFs (ex: Smallest File Size, High Quality Print). I've checked all the print settings under "Print Booklet" including (Print Booklet -> Print Settings -> Setup -> Adobe PDF (Preferences))

Question

What are these lines and how do I get rid of them?

Including an image to help show what I am talking about:

Answer 1

Flattening.

Depending upon the job options set, the PDF may be flattened to aid in reproduction. Flattening can often result in these hairlines which will disappear or move when you zoom in. These are basically anti-aliasing lines in the PDF between raster objects where transparency is altering appearance.

Here, "Print Booklet" won't generate a PDF, it prints. The only way to generate a PDF from Print Booklet is to either A) use the old Adobe PDF Print Driver. Adobe stopped production of this intentionally and it only generated PDF at PDF version 1.3 (Acrobat 4). Or, B) use the OS to "save" a PDF from the print screen. This is wrought with issues because the OS PDF generation (on either OS) is poor and designed for the "mom & pop" crowd, not reproduction. There are many aspects of PDFs the "save as PDF" command can not render properly.

It would appear that your left image (with hairlines) is a flat PDF most likely using PDF1.3 (Acrobat 4) or older. These hairlines will customarily disappear when the piece is actually printed. Using PDF 1.4 (Acrobat 5) or better to generate a PDF will not show the hairlines because PDF1.4 support transparency whereas PDF1.3 does not.

A better option may be to export the PDF using PDF1.4 and then create a new InDesign document and use File > Place to place the pages in printer spreads. Then export again. If you set things up this way, you can always edit the original document, re-export to PDF again using the same file name, and the placed pages in the printer spread document will simply update images. You can then simply re-export the printer spread document.

In short.... if you are using the Adobe PDF print driver to create a PDF from Print Booklet, that's your issue. That driver was killed for a reason. It's old and does not support layers or transparency so it must flatten everything.