I exported my PDF with images from Illustrator, but the file was too large (around 35 MB), so I exported it with the PDF/X-1a:2001 setting to lower the resolution. The file was smaller as I wanted, but I noticed that that the color in the images had lost a lot of vibrance and saturation and the images were just a lot duller. I would really like to know if there a way to prevent this from happening while also keeping the files at a relatively small size (like <5 MB)? Thank you!
PDF/X uses CMYK color, If your artwork is RGB, that’s why there’s a change. Distilling to PDF/X will auto-convert colors to CMYK in the PDF/X options.
Source : Link , Question Author : charliepodcast , Answer Author : Scott