The steps mentioned here is only to make it costly and difficult for anyone to modify (insert/delete) the contract signed between 2 parties.
1. Number each and every page and have a count of the total number of pages in the document. With the latest software, it is quite easy to even count the number of lines, words and character in the document.
2. Never use a black pen for signing the document. Always use a pen with a hard metal tip and press hard to ensure that the pen leaves a physical dent on the page.
3. Always sign each and every page of the document. Put your initials next to any changes and amendments.
4. Most importantly in the last, spread the sheet of paper as a Chinese fan/accordion so that only the ends of the pages are visible. Then sign on this fan. This makes changing only 1 page of your contract nearly impossible to photocopy or modify. So the entire document now has to be redrafted.
There are several hologram, smart papers, digital signature etc to protect the document. It all depends on cost vs benefit. One security measure you should definitely explore is depositing the contract with a Notary. It might cost as much as 500$ to deposit the contract but it’s quite secure.