Here are some PDF's of some interesting books. You are also welcome to contribute to this thread by adding PDF's of educational books.
Se Kinehiya (Punjabi)- https://www.vidhia.com/Sant Harnaam Singh Ji - Rampur Khera/Se_Kinehiya_-_Gurmukhi.pdf
Se Kinehiya (English)- http://www.gurukhoj.com/eBooks/Se_Kinehiya_-_English.pdf
Mahankosh (Punjabi)- http://old.sgpc.net/CDN/Mahankosh.pdf
Bhanu Prakash Granth by Sant Jagjit Singh Ji Harkowal Wale (Punjabi)- https://babaniakahaniya.