Ghunyat ul Talibeen (The Sufficiency for Seekers) Author: Abdul Quddus Gangohi (1476-1537 CE) Language: Arabic (with translations available in other languages)
Here's a brief write-up on the book:
I'm assuming you're referring to a PDF version of the book "Ghunyat ul Talibeen" (also known as "Ghuniyat al-Talibin" or "The Sufficiency for Seekers").