There's a Section on languages in the faq, esp. The section « How did colonialists talk with indigenous people? » and the thread on people speaking different languages might be interesting for you. I haven't seen a lot specifically on contracts there though, and can add to the Spanish American context for that, esp. on Mexico.

As mentioned in the threads above, pidgin languages (combining and ofqten simplifying various parts of the different languages in contact) usually develop in cases of prolonged intercultural contact, e.g. when trade is involved. However, this was not really necessary regarding land rights in the early phases of Spanish expansion, due to the requerimiento. This ritual involved a Spaniard (often a captain or other military leader) reading out loud a model text in Spanish to native people who didn't understand the language – it has often been called the « fiction of a contract » because of this subsequently. Moreover this decleration written in 1513 informed the native population of Spain's divinely ordained right to take possession of their lands and to subjqugate them. The latter's choice was also rather fictional : Either they could agree and become subordinate to Crown and pope, or disagree, in which case the Spanish Crown reserved its right to view them as heathens and fight them accordingly. So , a clear win-win situation... It's also interesting to note that (like many Spanish customs in the Americas) this practice had precedents in the medieval Iberian « reconquista » period, in similar edicts issued by Spanish Muslim rulers to Christians.

The requerimiento was of special importance in the earlier phase of Spanish conquest, in the Carribean but also Latin America. In later phases after initial contact interpreters and translators played increasingly important roles. The example of Cortés' campaigns in Mexico shows this, as translators like the Spaniard Géronimo de Aguilar and the Nahua noblewoman Malinche (to the Spanish « Marina ») made communication and thus alliances with various native population groups possible. Restall has a good discqussion of the rôle of interpreters in the conquests in his « Seven Myths of the Spanish Conquest » (ch. 5). He mentions that Aguilar who had been stranded in Yucatan spoke Mayan and Malinche knew Mayan and (the main Aztec language) Nahuatl but little or no Spanish – so that Cortés communicated with Nahuatl speaking lords through the triangle of his two interpreters. This system was clearly imperfect but still allowed for basic communication. Thus Restall challenges myths of both the Spaniards' 'superior' communication skills, and of suppesed extreme miscommunication taking place. Interpreters played silmilarly important roles in Pizarro's campagins in Peru, as well as in other Spanish American regions. Still, we can't speakq of « contracts » in the traditional European sense in the cases of the requerimiento and in the building of unequal alliances through translation processes.

Looking towards the mid- to late 16th c. in colonial Mexico there is on the one hand the great importance of the ecomiendas, whereby first conquistadors and later on other Spaniards received the right to labour of indigenous people on a certain territory – the conquistadors had actually mainly fought to receive such grants. On the other hand, the rights of native communities to their traditional lands were in many cases acknowledged by the Spanish Crown or viceroys. Such ackowledgement necessitated once more linguistic skills by native (and increasingly mestizo) people to translate between Spanish and native languages. While local communities often used maps drawing on pre-hispanic cartographical traditions with little or no text, native nobles wrote elaborate chronicles and letters to the Spanish authorities in Spanish, claiming the rights to their ancestors' lands and to higher posts. Such texts were connected to the rise of a lettered native elite esp. towards the late 16th c., many of whom had been educated by Franciscans in Spanish, Nahuatl and Latin – the Franciscans' motivations for this included learning more about native customs to aid in conversion, and (only at first) hoping to ordinate native priests. This process led to a lot of material that often managed to convince the colonial authorities of granting land rights, in many cases into the 18th c., rights that were in turn often again challenged subsequently. Gruzinski's Conquest of Mexico is a good starting place to read about these later developments.

Coming back to your question, I think that in the earlier stages of contact in the Spanish Americas we don't find contracts between Europeans and native people as the ones you described for the 17th c. Dutch colonies (which contracts I'm not too familiar with, although I could imagine pidgins playing a bigger role in their case). Here the requerimiento played a major rôle in transmitting Spain's supposed divinely ordained rights to the lands, and native translators further aided in Spanish military campagins. At least in Mexico towards the mid-16th c. the titulos primordiales (for commoners) and chronicles (for nobles) in many cases regulated the continued possession by indigenous people of traditional lands, although they were not always granted – by this time translators fluent in Spanish and native languages, as well as crucially in the Latin alphabet were more common. Then again, rights to native labour continued to be granted to Spaniards through the ecomienda system, later replaced by the repartamiento system. I didn't write in more detail because of troubles with the keyboard, so let me know if anything's unclear.