I produce a quarterly magazine using Serif PagePlus X6. I also use it for a two sided weekly news-sheet and have used it for large (64 page plus) booklets. The export to pdf is very useful and I wouldn't move to anything else for the type of job you want. Any 'upgrade' is likely to more towards a commercial piece of software which could be quite expensive.
Surface Pro 4 UK release date, price and specs: Thinner, lighter, faster with new Type Cover and Pen