Based on your query, both Nolej and Quizlet could be useful for creating flashcards from your PDF textbook vocabulary.

Nolej is an AI tool that can convert your existing content, such as text documents, into interactive "micro-learning packages." This includes flashcards, which could be ideal for your needs. You can easily upload your PDF textbook, and the tool will auto-generate the flashcards for you. This could save you a lot of time and effort. Plus, Nolej integrates with popular learning platforms like Google Classroom, making it easy to share these flashcards with your students.

On the other hand, Quizlet is a platform specifically designed for creating and finding study sets, including flashcards. You can customize the content to suit your classroom needs, which could be beneficial if you want to add specific details or context to the vocabulary words. Quizlet also offers various study modes and tracking features, which could help enhance the learning experience for your students.

In conclusion, if you're looking for a more automated solution, Nolej could be the way to go. But if you prefer to have more control over the content and presentation of the flashcards, Quizlet might be a better fit.