Sorry for the later reply!
Seems my previous reply is failed to the post.
About the K21 and K40 schematic, you can refer to the related FRDM board or the Tower board:
Find your chip's related refer board, then check the schematic.
About the pin information, you need to refer to your chip reference manual, we have a chapter about the pin assignment, you can refer to it.
Wish it helps you!
If you still have questions about it, please kindly let me know.
You can find the information you're looking for at nxp.com. Start out by doing a search on the parts you're interested in.
For pin information (electrical and physical placement) look for the part number's "datasheet".
For electrical operation and a description of the various functions of the devices look for the part number's "Reference Manual".