work visas cannot be obtained while in brazil on another visa - theyhave to be issued outside of brazil by the consulate of the country of residence of the applicant - so should the applicant already be in the country, he/she will have to leave and re-enter under the new visa, and of course register with the Federal Police (Polícia Federal).  

finally, there is also a business visa for foreign citizens travelling to do business but not to seek employment.  

seeking employment or working while in brazil under a business visa may result in deportation and fines.