I assume you mean you can't find a printed version of the 7th edition online, because the PDF is readily available from the Tektronix website
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/wink.gif)
. I remember before the Tektronix acquisition, Keithley mailing me a printed copy of the guide just because I had entered my address details to download the PDF. I think this was the 6th edition. I doubt they do this anymore unless you are a regular customer.
The changes between the first few editions were quite substantial due to available instrumentation. Like the original edition (which was something like "electrometer measurements") was published before source measure units when analog dials were still common. But I think the updates to last few editions just cover the newly introduced instruments. Comparing the PDF copies I have of the 5th and 7th edition, it appears that the main differences are the instruments that are used in the examples, the features they highlight and obviously the instrument selection guide. The 7th edition also contained a few more application examples.