Command Split

To split large file into several smaller files, you can use the split command:

split --bytes=10280k Calculus-Book.pdf Calculus-Book_

You can use b, k, or m. b represent bytes, k represent kilobytes, m represent megabytes.
To restore the original file, you can use cat command.
To join all the smaller file to restore the original file type:-

cat Calculus-Book_* > Calculus-Book.pdf