No. Disney has only officially published Journal 3 (hardcover and special edition) and Don't Color This Book! (which is technically Journal 2’s coloring book cousin). There is no official Gravity Falls Journal 1 PDF from Disney Press.
Journal 1 is the first of three mystical diaries written by Stanford Pines (The Author). Ford began writing this journal shortly after arriving in Gravity Falls, Oregon, in the mid-1970s. It contains his earliest anomalies research, engineering blueprints, and initial impressions of the town's strange properties. History within the Show Gravity Falls Journal 1 Pdf