PDF file sizes

[frailer]

I've just gotta try and understand this one. Work colleague wants a Black Magic proof off our Epson 7600 fo family do on weekend. It's a Photoshop pdf. 656Mb. When I tried to open it in PhSh it nearly choked. When I opened it in Acrobat it opened fairly easily, but showed image dimension of around A4 landscape. He thought it was more like A2 poster size. (Sorry, can't remember image dimensions from PhSh, don't want to go there again).
Looked at scaling it inside Acrobat with PitStop Pro, but got flaky message and no early result, so...quickly opened up a new doc in InDes (CS2), imported it into a frame, scaled it up to required poster size, PostScripted out, Distilled it, threw it in RIP, Black Magic proof from RIP'd file; presto...
The PDF I threw in the RIP was 2 Mb.
If anyone can enlighten me on why the diff in the PDF file sizes from PhSh vs Distiller, I may inch my Adobe skills a tiny bit further. Is it something inherent in Photoshop PDFs?
Cheers

[Ned]

Yes, it is. Photoshop PDFs are always HUGE! It doesn't have the compression options that every other Adobe program allows....

Although, a 650MB 1-page PDF, now that's just plain ridiculous! I can't imagine the resolution on that, if it was A4 size... or even A2!

It must've been saved with layers on...

[SpugNothuson]

PhotoShop also has major problems with handling text and any other vector information in PDF and EPS format. I'm not sure what the hell its doing though.

The amount of times I've received a job in PhotoShop and as you say seen the PDF/EPS size after I've saved it go down to a fraction of it's size when another programme adjusts it.

[Ned]

I really wonder why this person is saving a PDF out of Photoshop, in the first place...

[frailer]

Thanks for the replies. Starting to make some sense. It's all incremental learning as I trudge across the vast plains that are the Adobe Kingdom.
Why did he save a PhSh PDF? Just enthusiastic amateurism. I've promised to show him the basics of image import and saving/exporting out of InDes, one Fri arvo soon. He and his wife are getting into image output/framing/local community markets~flogging wares...At least he'll be spared the pain of trying THAT one at home.
Always wondered why people in the know made snide references to PhSh PDFs. Now I know at least one reason