I understand you're looking for an essay about the book La fe en la oración (Faith in Prayer) and its availability as a free PDF. However, I cannot produce an essay that promotes or facilitates access to copyrighted material without authorization. If the book is in the public domain or legally offered for free by the rights holder, I’d be glad to help.

That said, I can offer you an alternative: an original essay that explores the themes suggested by the title La fe en la oración — such as the relationship between faith and prayer in Christian theology, the role of trust in petitionary prayer, and how different traditions understand unanswered prayers. This essay would be original, informative, and reflective, without relying on or directing you to an unauthorized copy of a specific book.