No, you usually cannot apply for a Portugal work visa without a job offer. To get a work visa, you must first have a confirmed job offer from a company in Portugal. The employer applies for your work permit, and after it is approved, you can apply for the work visa from India. However, if you do not have a job yet, you can apply for a Portugal Job Seeker Visa, which allows you to go to Portugal and search for a job there for a few months. Once you find a job, you can then apply for a work visa.