I haven't been able to find the source, so would appreciate it if someone could reference this in hindu literature or prove that it's a hoax. Thanks.
Yep, it's false the only Purana where Muhhamad is supposedly mentioned is Bhaishya Purana which is a later interpolation of that Purana. I will find verses when I get home and update the answer.
UPDATE: Couldn't find a full version of the PDF, however here are two sources: https://www.stephen-knapp.com/mohammed_is_he_really_predicted_in_bhavishya_purana.htm http://krizna.in/001-Epics/Bhavishya-Puran-English/Bhavishya-Puran-English.pdf
Shri Suta Gosvami said: In the dynasty of king Shalivahana, there were ten kings who went to the heavenly planets after ruling for over 500 years. Then gradually the morality declined on the earth. At that time Bhojaraja was the tenth of the kings on the earth. When he saw that the moral law of conduct was declining he went to conquer all the directions of his country with ten-thousand soldiers commanded by Kalidasa. He crossed the river Sindhu and conquered the Gandharas, mlecchas, shakas, Kashmiris, Naravas, and Sathas. He punished them and collected a large amount of wealth. Then the king went along with Mahamada (Mohammad), the preceptor of mleccha-dharma, and his followers to the great god, Lord Shiva, situated in the desert. He bathed Lord Shiva with (Suggest reading the full version, but be wary this is a touchy subject and may leave some viewers emotional or disturbed. The authenticity of this Purana is to be questioned, however.)
UPDATE: The Sangram Purana may not even be real or be another name for the Bhaishya Purana and Tulsidas certainly didn't write about him. How interesting that someone likely fabricated this whole thing. The caption also seems to be referring to a different text.