In marketing and sales, marketing collateral is considered the collection of media used to support the sales of a product or service. This is how Wikipedia defines marketing collateral.
Marketing material or brochures, sales communication are meant to be read by your existing and prospective customers. They get information about your product and importantly get engaged with your brand.
Your catalogues, product information, brochures, handouts educate the customer to make informed decision to choose your product over other options available.
Naturally, it has to speak the customer's language. The business needs to plan the languages of communication to the customer. Certain pointers to make the exercise easy :
Which is the geography where the collateral will be read?
What is the educational and occupational background of the prospective users of my product or service?
What is the primary role of this collateral? Information, education, motivation or persuasion ?
Are the readers monolingual or bilingual ?
The next step in language planning is to decide if the collateral can be plainly translated or need localization or need to be rewritten in the target language.
People from different regions think differently and value systems in different parts of the world are different. Buying decision is influenced by different factors.
The business need to evaluage the degree of difference in the original and target market and thus arrive at the decision about translation, localization or re-writing.