. While JEDEC members can download it for free, non-members are often required to pay a fee (approximately ) to help cover production costs Authorized Retailers: Platforms like the Accuris Standards Store GlobalSpec provide purchase options for the PDF signal assignments from this standard for a design project? DDR4 SDRAM STANDARD - JEDEC
If you have the document open, these are the most technically "dense" sections usually found in JESD79-4D: jesd794d pdf