I am trying to create a document with pages that have a set number of lines, size of text, and leading. I would like to justify it vertically by having InDesign automatically adjust the word spacing to fit the text into all the lines in the frame. Is that possible?
Are you asking how to vertically justify the text frame content (aligning the top line with the top of the frame, and the bottom line with the bottom of the frame) without InDesign feathering the leading?
Define a baseline grid
Snap all content to the baseline grid
Disable keep options
Resize the frame to a multiple of the baseline grid value