No template as such.
If it were my project I would have the letters with one letter per PDF file, so if a letter was 3 pages long I would have all three pages in the same PDF file.
I would then have one letter per Post, with a short summery of the letter to give people an idea of the contents of the letter. A paragraph or so of text for visitors
I would start Posting them in chronological order - first letter first second letter second and so on - that will then show up in your blog as last Post at the top - THIS IS GOOD - as regular visitors to your site will see the most recent letter at the top
You can load the PDF file into your media library and have a link in the Post to the file. Or you can insert the letters using Scribd (see below) that will then display the letter in the Post so that visitors can read it or open it in Acrobat (or save it to their PC for later (both methods let the file be saved) )
A caution on Scribd, it will load the whole PDF document each time it is displayed, so you need to have the Scribd document after a "more Tag" or you will kill your load times and nobody will want to visit again.
that should get you started - good luck with your project, I have started a similar one for some of my working in Alaska in the 60's & 70's and going back to Jr. High School days also -