Bob Swanson offers a number of his books
in electronic formats. This web page describes how to
view the Adobe Portable Document Format (PDF) files published
Examples of such book offerings include:
Bluejacket Mail, A Postal History of the Great Lakes Naval Training Center in the First World War
Domestic U. S. Military Facilities of the First World War, 2nd Edition
If you order one of these books in PDF format, you will receive a file containing the book, or a link from which you can download the book contents. Store this file on your computer or phone/tablet.
The PDF format is a standard, and is pretty much world-wide in use. It was originally created by the Adobe Corporation. When viewed, a PDF document appears on your screen as close as possible to its appearance on the printed page. Note that Bob Swanson's books are stored in PDF format as 8 1/2 x 11 inch pages, not A4 or any other European standard.
On most systems, double-clicking on the PDF file should bring up a viewer for the document. On many computer systems, the reader is the Adobe Reader program. There are several other readers available for computers, phones, and tablets. One example is the Foxit reader, provided by a commercial company for free. When downloading a program like this be sure you are connected to the vendor website, and not just any "free downloads" website, as some so-called "free" sites can try to load dangerous software into your computer or phone.
PDF is a powerful document system. For many documents you read, you will not see all the features it offers. A lot depends on the author or PDF creator.
Bob Swanson offers his books in two PDF formats:
1) Printable PDF -- this book format is ready to print as an 8 1/2 x 11 inch printout. It can be viewed in the PDF reader (see below), but will not contain bookmarks or links. You may print a single copy of the PDF for your personal use. Do not try to take this PDF file to an "instant print" store, as they will not print a copyrighted book, unless you are the author.
2) Interactive PDF -- this book format is intended to be read in the PDF reader, and contains fully interactive content. It is not intended to be printed on paper.
One of the features of the PDF format, is the setting of "bookmarks" within a file. When you view the "interactive" version of a book, you will see the pre-set "bookmarks" along the left side of the display screen. These were put in by Bob Swanson, the author, to allow you to navigate to different pages of the book. If you don't see the bookmarks, try to enable them with the "View" menu of your PDF program.
You can always search most PDF file for text values, using the PDF reader program. For instance, looking at one of Bob Swanson's books, you can search for the string "great lakes", and you should see all the references in the book for that military facility.
Many PDF readers offer a list of "thumbnails" along the left of the display. These little images show each page of the document. It may be easier for you to navigate around the document, using these thumbnails, rather than using the scroll mechanism of your computer.
As noted above, Bob Swanson's books are available in fully interactive PDF format. That is, as set up, there will be clickable links within the book that not only jump to a particular part of the book, but can also jump to a web page in the internet. The Index and Table of Contents in the Interactive PDF books are created as clickable links. (In the printable PDF book, all references are to page numbers, there are no interactive links.)