[Gimp-user] Printing a poster file issues

[big__dav <forums gimpusers com>]

Please go easy on me as I have not done anything like this before and I am sure
I am making a stupid mistake somewhere.

I need to create a poster that is roughly 1.3m x 2m and the printer requires at
least 300 DPI.

I have created my poster in GIMP and it consists of 7 layers - x1 large picture
that fills the poster and several other small logos/pictures/text.  The pixels
per inch setting in GIMP was set as 350.

The GIMP file is roughly 687Mb and when I export it to a PDF the PDF file is
roughly 375Mb.

When I try to open the PDF file in Adobe Reader DC I get an error - out of
memory and the file does not open.

GIMP version - 2.8.18
Adobe Reader DC version - 2015.020.20042

When I export to PDF from GIMP I ensure that the options to ignore hidden layers
is ticked and also that the option to convert to vector data type if possible is
ticked.

After getting stuck here I removed the hidden layers from the GIMP file ie
deleted them - they are used for alignment and information when designing. 
After this the file size was very slightly smaller and Adobe Reader could open
the file.  However when I tried to print it out in A3 sheets to check to see how
it looks Adobe hung up on the flattenning stage.  So I then went back to GIMP
and flattened it in GIMP so that everything was combined into one layer.  Now
when I go back to Adobe to print I have no hanging up on flattening however it
hangs up on "print 0%".  When I check the task manager Adobe is using up plenty
of processing so it is doing something...

Having no experience in doing something like this I dont know if the file sizes
involved are "normal" or not.

Can someone tell me if the file sizes I am experiencing are to be expected - I
would assume they are.
Should I be able to print a PDF this size out?
Can anyone see anything that I am doing wrong?
Can anyone suggest how to get my PDF file out and that will be able to be
printed when sent to the printer?  Would a professional printer have some sort
of software that will allow them to print a PDF  that I can't print?

-- 
big__dav (via www.gimpusers.com/forums)