If you want to calculate the cipher on paper everything that works on binary will be a huge overhead and basically require you to write stuff down for the calculations. So you need to burn sheets of paper for every en/decryption. So no XOR or anything.

I would go for a stream-caesar-cipher. Find a mathematical formula that you can calculate in your head and that gives you a numbers between 1-35 (or something similar depending on how many different characters you need). The formula must be pseudo random so f(x)=5, f(x+1)=1, f(x+2)=28, … and not loop for a looooong time. Calculate a new value FOR EVERY LETTER OF YOUR TEXT!!! and use that as your Caesar cipher for that letter only (x is the position of the character in the text)

You need to keep track which letter in your cipher text was encoded with which x (write the x of the first letter of each page down) and keep the formula a secret. Never ever under any circumstance reuse an x. So you need to keep x going for every page/message and can’t restart at 1 each time.

If x becomes to large and the calculations to complicated, its better to change the formula than to restart x. Never ever ever ever reuse the same cipher because then you get all the drawbacks of Caesar ciphers (probability of letters, length of words (position of the space character) etc).