What does «suscribir» mean in Spanish?

To sign at the end or foot of a document.

Examples of use in Spanish: "suscribir un contrato".

"los que abajo suscriben", este uso es incorrecto por tratarse de una redundancia, suscribir ya implica abajo, por lo que debería ser simplemente "los que suscriben".
To agree with one's opinion.

Examples of use in Spanish: "suscribir una opinión".
Subscribing to a newspaper, publication or other service.

Examples of use in Spanish: "suscribirse a una enciclopedia".
To obligate oneself to contribute with others to the payment of an amount.

Examples of use in Spanish: "suscribirse por mil pesos anuales".