The method described certainly can be made to work ... but it's perhaps overly complex. Word has much simpler tools built in.

Line numbering is a very common requirement in legal contract work, depositions and court reporting, screen-writing and some other professional uses of Word. It is built in and very easy to use:

See Word Help:
------------------------------
Add line numbers to an entire document

On the File menu, click Page Setup, and then click the Layout tab.
In the Apply to box, click Whole document.
Click Line Numbers.
Select the Add line numbering check box, and then select the options you want.
--------------------
An average page of double-spaced text in 10 or 12 point fonts is 25 lines ... and if submitting work to a publisher double spaced is almost always what they want.

So I would first do as you suggest, turn off "widows and orphans", type what I needed to say ... fiddling with lines per page while creating sounds counter-productive, Then turn on double line spacing and turn on line numbering. I tried this on a couple documents and the adjusting to get 25 lines per page is very easy, at worst just a couple clicks in or out on the default side margins.

You can print the document with line numbers on, or save and turn line numbers off before printing as required by your customer.

Hope this helps
Dave

Good tip, Dave, but you're solving a different problem. Getting numbered lines is straightforward, as you say. Getting to have a fixed number of lines on each page is considerably more tricky.

Actually, Dave, Dave's (This could get confusing!) solution makes use of Word's line-numbering feature to avoid both the calculations in your solution and the necessity of counting lines in the OP's current practice.

Dave (Starr) makes this clear in his last two paragraphs.

One thing that's not clear in his post, though is how adjustments to the 'side' (ie. left and right) margins changes the number of lines on a page. My choice would be the top and bottom margins, with the larger change assigned to the bottom margin.

Also, assuming Word permits saving empty documents with assigned margin, spacing, font and size settings, the last step in the process would be to delete the text from a copy of the document, then save it as a template for future use.

Regards,
Barry

Can anyone help? I am trying to figure out how to do cascading text in Word
so that the paragraph will look like an inverted triangle where all the lines
in the paragraph are centered, but the margins keep decreasing slightly for
the next line, etc.

how to cascade paragraph or text in ms word?
How to make a financial table in word?

This is a bit late to help the original person, but in case anyone else would like to know ...

Word does indeed have a feature for specifying the number of lines per page (often called a "baseline grid" in typography or design circles). This divides the usable portion of the page into a fixed number of lines or spaces, and sets the type (wherever possible) within those lines.

The feature is not normally enabled in Word. That's because Microsoft implemented the feature for certain languages that absolutely require it, such as Japanese. In order to access and use the feature, you must tell Word to install those features (even though you won't actually type Japanese, of course). The instructions for enabling it may be slightly different for Word 2003 and Word 2007. Here are the instructions for Word 2007:

1. Shut down Word.
2. Go to Start > Programs > Microsoft Office > Microsoft Office Tools, and select Microsoft Office 2007 Language settings. (This for Windows XP. For Vista, the navigation may be different.)
3. In the dialog, navigate through the left pane (Available Editing Languages) and select an appropriate language (I recommend Japanese, since I know it works).
4. Click the Add button, so that Japenese is added to the right pane (Enabled Editing Languages). You will probably see a message or note that the language is available only with "limited support". Ignore this (it just means that Windows isn't set up to use a Japense keyboard).
5. Click OK. If you see any more notes about limited support, close or cancel them. They don't matter.
6. Start Word.
7. Click Page Layout > Margins > Custom Margins. This opens the Page Setup dialog, which usually contains three Tabs: Margins, Paper, and Layout.
However, you should now notice that a new Tab has been added, called Document Grid.
8. Select the Document Grid tab. Under Grid Options, select "Specofy line grid only".
9. Under the Lines option, specify the number of lines you want per page. Tip: if your document is divided into sections, and you want to apply this setting to the entire document, make sure to select "Whole document" in the "Apply to:" list at the bottom of the dialog. Then click OK to exist this dialog.
10. Note that Word's normal Line Spacing options, such as "single", "double" and "multiple", now become relative to the grid (instead of to the pointsize of the type). That is "single" will set the text using single grid lines, "double" will vertically center each line of text over two lines of grid, etc. All the usual caveats of using grids still exist: if you use a pointsize larger than one grid line, Word will automatically use multples of the grid. (So if your grid works out at about 18pt, and you use 24pt type, each line will be centered vertically over 2 grid lines).
11. With grid lines, it makes no sense to use above/below paragraph spacing based on points or inches. If you do, the type will be pushed off the grid. If you want extra spacing, it should be measured in "lines". Word allows this. For example, I have a style that I use for scene breaks in novels, where I want one extra line of space above the paragraph. This is specified as "1 line" (without quotes) in Paragraph Spacing: Before. You can specify "2 line", "3 line" (the word line is always singular). Word takes this to mean "lines of grid spacing". You can specify fractional lines, though of course that will push the type off the grid.
12. Here's a tip if you sometimes use larger type and want the following text to re-align to the grid. For example, I set chapter headings in 24pt. My basic page is 30 lines (works out about 19.2pt), and my normal body size is 11pt. I start each chapter as a new section (using the Section: Next Page, Section: Odd Page, or Section: Even Page options). I want my text to start half-way down the page, with the chapter heading centered vertically in the space above. I experimented with various "Space before/after" options and found none of them worked properly: my body text always fell off the grid! Then I worked it out: for the chapter heading, do not specify any space before/after the paragraph. Instead, specify the Line Spacing option (under Paragraph Formatting) as "Multiple", then enter the number of grid lines that you want the heading centered over. In my case, that was half a page, which is 15 lines. So I specified the heading to have a Line Spacing of Multiple: 15. Works perfectly!
13. If you want to see the grid lines on screen, turn them on using View > Gridlines.
14. One final note: the number of grid lines that you specify, is literally the number of gridlines between the margins. Headers and Footers fall outside this grid. But the main point is that the number of lines of text is always one less than the number of gridlines. So if you specify 30 grid lines per page, you will get 29 lines of type. That's because in Word, these are not strictly "baselines". The visual effect is the same, but these lines mark the upper/lower bounds of each text line. So the first gridline marks the top of the first line of type. The second gridline marks the bottom of the first line of type, and the top of the second line. The third gridline, marks the bottom of the second line of type (and the top of the third). So each line of type requires two gridlines. Therefore, if you want 30 actual lines of text on a page, set gridlines to 31. If you 28 lines of text, set gridlines to 29. Gridlines is always "lines of text, plus one". Lines of text is always "gridlines minus one".
Cheers!