I am wondering how it's possible to define my own (length & width) dimensions when creating a pdf file (in tab 'book') from a selection of my photos? Right now, I am only seeing the few formats that are being given by Blurb, even though I chose 'pdf' in the dropdown.
I'd like to create a pdf that is following the dimensions from my pictures - with the given Blurb-formats, I am seeing white frames on top & bottom of the pdf-file. I am sure there must be some solution to this.
No solution! The Blurb Page size presets are fixed in Lr-Classic, and the 'pdf' dropdown option will only 'Export' the book pages as the available page dimensions.
You might Export files, or use the Print module to [Print to File...] JPGs of your photos, then use other software (Adobe Acrobat?) to create a PDF from the JPGs. (Mac computers have a PDF option in the Print dialog)