我几乎用 KOMA-Script 来处理所有事情，包括信件。当我使用 A4 纸时，这很轻松，但当我尝试使用美国信纸时，问题就开始了。
有了scrartcl类，\KOMAoptions{paper=letter}就可以达到目的。
与scrlttr2班级一起：
如果使用默认的类选项文件（DIN.lco我相信），则\KOMAOptions{paper=letter}无效。该文档编译时出现以下警告：
Class scrlttr2 Warning: Letter option file `DIN.lco'
(scrlttr2) needs paper size `a4'.
(scrlttr2) Current paper size is not `a4'!
(scrlttr2) You should add `paper=a4' at the
(scrlttr2) option list of \documentclass!
(scrlttr2) Maybe you know what you are doing,
(scrlttr2) so I do not change this myself.
输出为 A4。
如果我使用UScommercial9.lco 没有 paper=letter，编译时会出现以下警告：
Class scrlttr2 Warning: Letter option file `UScommercial9.lco'
(scrlttr2) needs paper size `letter'.
(scrlttr2) Current paper size is not `letter'!
(scrlttr2) You should add `paper=letter' at the
(scrlttr2) option list of \documentclass!
(scrlttr2) Maybe you know what you are doing,
(scrlttr2) so I do not change this myself.
如果我使用UScommercial9.lco，如在这个 MWE 中：
\documentclass[UScommercial9]{scrlttr2}
\usepackage[english]{babel}
\listfiles
\KOMAoptions{paper=letter,fromphone=true,fromfax=false}
\begin{document}
\setkomavar{fromname}{Stephen Bosch}
\setkomavar{fromaddress}{10 Lemon Lane \\ Sour Orchards BC V0E 0B0}
\setkomavar{fromphone}{+1 250 377 4141}
\begin{letter}{Tremulor Nocharme \\ Compliance Officer \\ Special TPS Police
\\ Fram Jammer Building \\ 320, 220 -- 4 Street \\ Treacleton AB T0M 0M0}
\setkomavar{subject}{Late TPS reports 2008, 2009, 2010, 2011, 2012}
\opening{Dear Mr. Nocharme,}
Attached please find the TPS reports you requested. Please accept my apologies for the delay.\\
\closing{Sincerely,}
\end{letter}
\end{document}
我不再收到警告，但输出是仍然A4。
此外，当我尝试通过删除
\usepackage[english]{babel}
行，我收到一系列非常奇怪的错误：
! Undefined control sequence.
\select@language ... \@empty }\languageshorthands
{none}\babel@beginsave \cs...
l.8 \begin{document}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
! Undefined control sequence.
\select@language ...me \relax \babel@savevariable
\lefthyphenmin \babel@save...
l.8 \begin{document}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
! Undefined control sequence.
\select@language ...hyphenmin \babel@savevariable
\righthyphenmin \expandaft...
l.8 \begin{document}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
Class scrlttr2 Info: used language is `english'.
(scrlttr2) Supported languages are `english', `UKenglish',
(scrlttr2) `british', `american', `USenglish',
(scrlttr2) `german', `ngerman', `austrian', `naustrian',
(scrlttr2) `dutch', `italian', `spanish',
(scrlttr2) `croatian', `finnish', `norsk' on input line 8.
注意：即使我删除了所有输出文件（包括 aux），我还是会收到此错误！据我所知，KOMA-ScriptDIN.lco不需要 babel，但错误消息表明某处有 babel 残留。如果是这样，我不知道在哪里，因为我在编译之前删除了所有我能看到的。我读过这个帖子和这个帖子已经。
所用文件（来自\listfiles）为：
*File List*
scrlttr2.cls 2012/07/29 v3.11b KOMA-Script document class (letter)
scrkbase.sty 2012/07/29 v3.11b KOMA-Script package (KOMA-Script-dependent ba
sics and keyval usage)
scrbase.sty 2012/07/29 v3.11b KOMA-Script package (KOMA-Script-independent
basics and keyval usage)
keyval.sty 1999/03/16 v1.13 key=value parser (DPC)
scrlfile.sty 2012/06/15 v3.12 KOMA-Script package (loading files)
scrsize12pt.clo 2012/07/29 v3.11b KOMA-Script font size class option (12pt)
typearea.sty 2012/07/29 v3.11b KOMA-Script package (type area)
DIN.lco 2012/07/29 v3.11b KOMA-Script letter-class-option
UScommercial9.lco
***********
如果相关的话，我在编译时使用 XeTeX。
答案1
请尝试以下 MWE（我稍微更改了您的 MWE）。它应该可以满足您的要求：
\documentclass[UScommercial9,paper=letter]{scrlttr2} % <==== changed
\usepackage[english]{babel}
\usepackage[pass]{geometry} % <==== changed
\KOMAoptions{fromphone=true,fromfax=false} % <==== changed
\begin{document}
\setkomavar{fromname}{Stephen Bosch}
\setkomavar{fromaddress}{10 Lemon Lane \\ Sour Orchards BC V0E 0B0}
\setkomavar{fromphone}{+1 250 377 4141}
\begin{letter}{Tremulor Nocharme \\ Compliance Officer \\ Special TPS Police
\\ Fram Jammer Building \\ 320, 220 -- 4 Street \\ Treacleton AB T0M 0M0}
\setkomavar{subject}{Late TPS reports 2008, 2009, 2010, 2011, 2012}
\opening{Dear Mr. Nocharme,}
Attached please find the TPS reports you requested. Please accept my apologies for the delay.\\
\closing{Sincerely,}
\end{letter}
\end{document}
诀窍在于您的tex发行版具有 A4 标准纸张尺寸。使用命令，\usepackage[pass]{geometry}您可以建议 LaTeX 使用 MWE 给定的纸张尺寸。使用 pdfLaTeX 和 XeTeX 它可以工作。
更新：
我不知道 KOMA-Script 选项pagesize（感谢 @Josef），它还会强制 LaTeX 用给定的纸张大小（这里是 letter）编写 pdf 文件。因此，您可以将我的 MWE 更改为（仅更改第一行）：
\documentclass[%
paper=letter % paper size
,pagesize % force given paper size in pdf
,UScommercial9 % Beta version for testing
]{scrlttr2}
\usepackage[english]{babel}
\KOMAoptions{fromphone=true,fromfax=false}
更新 2：
由于 KOMA-Script 3.17 选项pagesize是默认选项。因此您无需明确设置或加载它geometry（@Schweinebacke 的评论）。