PDF workflow edit makes file size larger

[scott pagan]

we have a customer that provides print ready PDFs that we typically proof and print. i had a few that the bleed was not saved properly. trying to save deadline time by fixing myself vs going back to customer or original designer to modify. when i opened them in illustrator (cc15/3.0.0), and File>Document Setup>enter (x amount) Bleed, and Save file, the file size goes from original 9.8mb to 136mb. it is a bus shelter ad backlit with high res product image, vector logos, and text with special effects (drop shadows etc). i've played with a simple "Save", "Save as", and testing with each of the default options from the pull down on the PDF save menu (default, high quality printing, press quality, and smallest) and get varying file sizes after save from 24mb up to 136mb. the "smallest" compresses the large high res images to an unusable print resolution and the render intents of the shadow effects do not match, leaving the ghosted gray/white box... so that option will not work for print production. i've tweaked the advanced options and still cannot figure out why i am seeing such file "bloat". i would like to be able to find an easy way to edit the bleed without having to open in illustrator in case opening the PDF needs fonts not installed (or i just don't have), or the file trying to re-link high res images not provided, etc with having only the PDF to work from. it's not bad with this one group of files, but i tried it on a larger file as part of my testing and that open/edit/save took the original PDF from 68mb to 371mb, a huge difference that would tie up more storage and slow down RIP processing to printers if this were a majority of my workflow for that day.

how would you handle this?

am i making too much of an issue of file bloat from original?

any tips to making the edits and saving so file size is in same general range as original?