Sharing a large PDF to someone on a slow speed internet connection, is like trying to drink a big milkshake through a straw...it takes a long time.
If you're teaching online, you'll want to be able to access and load your materials effortlessly and quickly.
The best way to do this is by keeping your PDF file sizes small so it's fast, even if the student has a slower internet connection.
1) The easiest way to keep your file sizes small (<1MB) is to break up you big PDF documents into smaller bits.
It's best practice because it's faster to load and will allow you to adapt to your students learning needs much easier.
Confusingly, a 2 MB file will take 8 seconds to load on a 2 Mbps connection (note its mega bits, not mega bytes per second). See here for a quick calculator.
2) Compressing your multi-page PDFs through a free service like ilovepdf.com
Not only can it reduce the size of your file to 1/10th but you have the added bonus is that this process also minimises the chance of the file being corrupted or not displaying properly (for example we have very occasionally had Japanese students have a problem with certain fonts).