OK, the kerning problem seems to be isolated to my signature font. The attached example in another font seems to work. I guess my signature font may be underspecified in some manner. In any event, I have solved my signature positioning problem by using a different number of spaces for different signatures.
HOWEVER, the attachments shows a problem with line spacing. (I will attach the Word output to the next reply.) I am using Times 11pt text throughout with Single line spacing, and the PDF output text ends up about 1" longer than the Word output for a page of text. I found I can manually specify a point spacing for the text (say 11pt or 12pt), and then the outputs would match, but not if there is no specification or Single spacing specified.
ALSO, the points in the second section of this letter are specified as full-justification (no ragged right margin), but the PDF comes out with ragged right margin.
FINALLY, in the letter-head footer I use a table with 3 cells. The centering on the last address line (bottom right) is specified as centered, but is way out of sync with the lines above it. My guess is that centering is being calculated on the smaller font size used for the first word on this line, and that the larger font size used for the phone numbers causing the hang-over to the right. Is it not possible to mix font sizes?