Reduce the weight of a PDF before uploading it
The limit is 50 MB. A printer's catalog often exceeds it: its images are in 300 dpi, while a screen requires 150.
From InDesign
File → Export → Adobe PDF (interactive or print), then Compression: bicubic at 150 dpi, average JPEG quality.
From Acrobat
File → Save as another format → Optimized PDF. Set color images to 150 dpi.
On the command line
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -o small.pdf big.pdf
Two volumes are better than one truncated file
A catalog of 800 pages is divided into two volumes: each keeps its link, and you present them side by side.