Data Merge file using links with small file sizes exporting to vastly larger PDF

[Hydrolaze]

I have been struggling with a a data merge file for addressed envelopes. In the file I have an 84 KB AI file placed as the background (100% vector, no raster data whatsoever), and then a text box in the center of the page with placeholders that link to a 78 KB data file with 675 entries. I am trying to export a proof containing all data entries for a client to review, but despite using the "smallest file size" setting for export and the very small file sizes of my links, the exported PDF is 11.6 MB. This is in excess of the file size limit for my email, and although I can use a file transfer service as an alternative, I would like to understand why InDesign is exporting such an unreasonably large file for future related jobs.

I have done a bit of research and I learned that the PDF specification contains a feature called the Form XObject that is designed for the purpose of including repeated graphics in a PDF file. I also found a forum thread from 2010 where an Adobe employee explicitly confirms that InDesign's data merge uses this feature:

"For what it is worth, the PDF export from InDesign's data merge already (since InDesign 6) does export fairly optimized PDF using Forms XObjects to represent repeated content, one of the major features of a PDF/VT file."

So based on this information it seems that there is no reason that this file should even be in excess of a single Megabyte! Bewildered, I attempted to reexport the file with the background graphic removed. Despite this change, the file still exported at 11.6 MB! I tried another export with the background reinserted and the font changed from Apple Chancery to the default Minion, and the file exported at 6.5 MB instead.

So it seems to me that InDesign is embedding the font glyphs in a way that uses much more space than it should, perhaps even re-embedding the glyphs for each separate page. Does anybody know what is happening and how I can prevent it from making my files excessively large?

[Jeffrey_Smith]

To minimize PDF file size of a data merge document try this:

- export PDF directly from data merge panel, instead of creating a merged document first

- export with Acrobat 8/9 PDF 1.7 compatibilty

[MW Design]

I'm not at a computer right now so I can test. I think form xobjects kick in if the background is on a master page. Might have also something to do with the pdf export type. But from Dov's reply, it may not require the pdf type be of a certain type.

Then again, my memory is hazy. I usually just upload large pdfs to dropbox and send a link to it.

[Hydrolaze · Accepted solution]

I figured out the answer. My text had a stroke to make it bolder. Because of this, InDesign had to outline the text on every page with stroked paths. This is why the file was so large; it was ~10 MB of extra paths.

I re-exported the file with no stroke on the text and it is now a very reasonable 703 KB. Still quite a bit larger than the data used to generate the file, but I understand that PDFs have some necessary overhead.