The more images the higher will be the used space, the better the quality the higher will be the used space. 54 pages with 120 images is much space.
What file types did you use? If you have vector graphics like logos, use AI or PDF/X-4, never use any pixel type.
If you have text, never outline it, keep it always as text.
For the form use only standard fonts, don't select some kind of specific corporate font as this will increase the size in a massive way.
For raster images use RGB (this is recommended also for print files in InDesign!!!!!!).
Export the PDF not as PDF (Print) but as PDF (interactive).
Yeah, I'm already aware of all the things you've pointed out. As I mentioned, the file size is large because of the number of images used, they're mostly jpgs reduced in size from .psd files. Graphics are vectors and text isn't outlined so it can be searchable online and Helvetica has been used in the form. The InDesign document was exported as an interactive pdf.
My questions remains - what is the best way to publish this file online while retaining an editable form page, reasonably high res images, but reduce the document size. There has to be a better way than an interactive pdf.
Try: File > Save as Other > Reduced File PDF...
There is no way to assure this will work in a browser as a PDF especially in light of all of the mobile devices and mix of high and lower quality displays.
For what you're describing, I'd split the information up into several pages in a website including the form. I certain would never consider using an interactive PDF for it.
One cannot legislate the size of a PDF file to fit some preconceived notion of what is too big. 54 pages with 120 images taking only 13.3MB is pretty good.
The only way to significantly reduce that size is to downsample images to lower resolution, use a more lossy compression (lower quality JPEG, for example), or both. Ultimately, you end up with content that looks terrible. (You should also remember that newer mobile devices and even desktop and notebook computer screens are increasing their resolution, in some cases up to 250+ dpi. Images downsampled to 72, 96, or even 120 dpi will look quite poor.)
You should also consider that many web pages these days download in excess of 2 to 4 megabytes of “stuff” before the web page is at all useful. In contrast, 13.3MB for 54 pages and 120 images is an absolute bargain!!!
One other thing that you should consider when creating the PDF file is to always use the “optimize for fast web view option” when creating the PDF file. That optimizes the ordering of the PDF file objects such that the content for the first page can be downloaded and displayed while the rest of the file is being downloaded!
Awesome, thanks Dov. This information is very helpful.
Knowing that 13.3MBs isn't so hefty for the web these days shines a bit of light on some areas of design/technology I need to catch up on - I'm a bit stuck back in the mid-2000's
Good to have your expert input.
One thing I'd like to ask you, I'm working on a 200 page illustrated book. If I export it to (say) PDF/X-4 it comes out at around 12.5MB. If I then File > Save as Other > Reduced File PDF... it comes out at 2.8MB – I get a warning "The PDF document contained image masks that were not downsampled." but this PDF seems perfect for circulating for proofing and for web use. So my question is, what has been lost to reduce the document size so significantly?
Personally I cannot recommend to use the command to save as file with reduced size if the original document is available. In my experience the quality of any PDF is always better if I use appropriate export settings from InDesign. In many cases I get smaller sizes when I export as PDF interactive, even if I don't use any interactivity. I use PDF/X-4 often but only for print or for the use to place file in InDesign or Illustrator, but not for providing in the web and never to have a small sized PDF at the end as PDF/X-4 contains so much information I don't want to provide to anyone.