¿Cómo rasterizar un archivo PDF? (How to rasterize a pedf file?)

You can protect your file, so that text can't be selected, printed etc without knowing a password. You can even protect a PDF so that the PDF file will not open without the correct password. You can't, however, avoid people doing OCR on the data, except when you make the data illegible. This is because OCR can be a detached option from Acrobat.

I'm not sure I understand this correctly, you should be reading this:

https://www.pdfa.org/resource/pdfraster-1-0/

¿Cómo puedo rasterizar ese archivo?

You can export as image (TIFF, PNG, etc).

para evitar que puedar reconocer ocr, seleccionar secciones etc

You will not be able to prevent it.