I have a simple ad that I built in Illustrator CC with one linked image. The file size of the AI file is 5.8MB, when I export to PDF (2001 with Printer Marks and Bleeds) the file size increases dramatically to 43.6MB! I have no idea why this is happening but it's been frustrating me ALL MORNING. I've never had this issue before when exporting to PDF. Can anyone please give me any tips!
[I;m assuming "PDF (2001 with Printer Marks and Bleeds)" refers to PDFX/1-a standards]
Flattening and embedding of data.
When you save an AI file to PDFx standards artwork is expanded and flattened, removing all transparency, embedding any raster images, embedding fonts, or font subset, actually "baking in" any object transformations, expanding patterns, etc.
Basically what the PDFx options essentially do is "print" the file to a PDF. So the resulting PDF is built upon the actual output postscript data.
The difference is, in Illustrator, Adobe can use application code shortcuts. Each file doesn't need to contain every line of postscript to output the file.
This is kind of similar to the "linked image" issue. When you open a file in Illustrator, it can see the image, see the reference to the original and then go get that data for you to use. Whereas in the PDFx format that data must be included, not merely referenced.
So Illustrator can save files size by including 4 lines of code to describe a shape, it's points, it's transparency, fill, stroke, transformations etc. But that 4 lines of internal application data, may take 4,000 lines of postscript to draw on output.
In terms of print production, files size is never a concern. All print destined files will always be larger in terms of kb/mb, and I mean always. No one cares how large the file size is for print files. What is of concern is quality. And for the high quality necessary for printing, you'll just have to get used to much larger file sizes.
When you save to PDF in Illustrator uncheck all options, especially 'Create Acrobat layers..' , but keep 'optimize for fast web view'. Make sure you don't have additional art boards in the AI file that gets dragged into the PDF, so save with 'use art boards' and specify only your current art board or the ones meant for export.
on a side note: If you have a linked file that you embed and then un-embed again, sometimes illustrator create huge files from those linked (image) files. Re-link the file to make sure this has not happened.
It's probably not down to the image. A linked 1MB image shouldn't blow up 40x times (unless you've turned image compression off entirely. If that's the case use ZIP compression).
Do you have a large amount of text in this print? Or some fancy vector effects? In short, Illustrator uses a 'short-hand' of sorts when storing text, or vector effects. When you save your .AI as a .PDF for print, those effects are converted to gradients and curves, and, with enough of them, can seriously increase your file size.
That being said, this could be caused by dozens of different issues. If you had a link to an image of the print we could give you a better answer.