Try to keep the document to 2 pages, 3 maximum. Really, even with 40+ years of experience, going in too deep detail of the roles you were in back in the 80's, be it valuable, isn't as relevant as your more recent experience.
The top paragraph needs to be an overview of who you are and what you bring to the table. I always recommend starting with your title and length of experience from the 3rd person.
A Senior Mechanical Engineer, with over 12 years of local experience working within the local building services sector. A driven professional with a passion for precision engineering and advancements in technology and innovation....
Start then with your most recent position, and work back from there, listing the company name, your position, and the dates employed. Have a paragraph of responsibilities, but focus less on tasks and more on achievements, and the impact you had on your team and the business.
Add in who you were working for client side, ie, the builder, the end user client and the project name. Also add in the projects value, and any notable info on the job, such as 'came in 2 months on time, and 200k under budget'.
Think about any external activities you are involved with, perhaps a team cycle club, charity fundraiser, or volunteering. Add in activity that says more about who you are and where your heart is.
Also, avoid repeating any tasks and duties in each employer section. Every job is unique, so it's always worth diving into them differences, and highlighting what you have learned and 'gained' from the experience.
If you have one, add it in. Everyone is on Linkedin now, and Linkedin itself showcases more about you. It's a massive opportunity to have an extension to your application, and an area where you can add a professional photo, and more information about you and what your passions are.
Get in contact with myself for the BPR team, and we can help you! We will ensure your resume is both relevant, and stands out in your market.