The calendar printing assistant uses a template with the extension *.catx. It's stored in the Office template folder, typically located at C:\Program Files\Microsoft Office\Templates. Locate the template you want to edit. Select it, press Ctrl+C then Ctrl+V to make a backup copy in the Templates folder.
My safe method: copy the .catx file to My Documents and open it with WinZip by right clicking on the catx file and choosing Open with... then browse for WinZip.exe. (If WinZip is not installed you will need to download and install it). Use the Explorer view in WinZip (View menu, Files by Folder) and locate the Content.xml in the Cal folder. Right click on content.xml and choose Edit to open it in Notepad. When editing is finished, click Save in Notepad (don't close it) then click on the WinZip window and approve the update. Copy the catx back to the Templates folder and approve replacing the catx in the Templates folder.
Faster method: Give your windows user account Modifiy permission to the Templates folder. Make a copy of the template then edit the original in-place.
You can leave the Calendar Printing Assistant open when you edit the catx. if you receive an error, select a different template. After copying the edited catx to the Templates folder, select the template to view changes in the CPA. If you need to make more changes, edit the file in Notepad, Save then copy the catx to the Templates folder and reselect the template in CPA.
Using
Predefined Colors, Fonts and Styles
Before changing colors by editing the XML, use the Color task pane to apply different themes. Colors and Fonts are applied in the XML with Style="style_name".
The following is a list of some of the valid attributes you can use. This list is by no means complete and is only intended to give beginners an idea of what can be changed.
To change the formatting within an individual day cell, look for the DAYFORMAT tag (may be near the end of the file) and locate the CalendarText tag under DAYFORMAT.
For example, in the standard monthly calendar 1
(Month_StandardMonth01.catx), day format is at approx row
87:
<DayFormat>
<Grid RowSetting="*" ColumnSetting="*" Height="Auto" Style="LevelLeafParent">
<CalendarText Row="0" Column="0" FontSize="24pt" FontWeight="Bold"
Text="#[%d]" FontFamily="style!FontMajor" VerticalAlignment="Bottom"
HorizontalAlignment="Right" >
I added VerticalAlignment="Bottom" HorizontalAlignment="Right"
to the calendar text row and changed FontSize to 24pt.You
can change FontWeight to Normal (other valid weights may be
supported, I only tested it with Normal).
The following screen shots show the original and edited template.
Days of the week
These are in the WeekHeader section in the <MonthFormat> (Monthly calendars)
<WeekHeader Orientation="Top" Height="0.3in" FontSize="10pt" Format="dddd" Style="LevelOneTitle"/>
This screen shot shows the font size used by the day of the week name set at 20 pt. You can use ddd for the Format if you want Mon, Tue etc.
Style="LevelOneBody"
in the Month Overview provides the lines visible in each square.
<WeekGrid Orientation="Fill" NumRows="Auto" NumColumns="7" LastRowMerge="2" Style="LevelOneBody">
Month and Calendar Thumbnails Section
do you wish you have more calendar thumbnails or had next month and the month after shown, instead of last month and next month? You can if you edit the Content.xml. This sample is from the standard monthly calendar but the process is similar for every calendar.
In this screen shot, I added 4 calendars, changed the grid background to
blue, the font size and color used by the month name after applying a color
theme.

<!-- For each thumbnail calendar you want to add, you need to add a column setting of 1.3in. Four calendars is pretty much the limit for portrait layout. Add background="color" if you want to change the background color of the Grid row where the Month name and thumbnail calendars are shown. -->
<Grid Row="1" Column="1" RowSetting="Auto"
ColumnSetting="*,1.3in,1.3in,1.3in,1.3in"
Style="Header" Padding=".08in"
Background="Blue">
<!--Month Title-->
<CalendarText Row="0" Column="0" Text="#[@TemplateDate_MonthNameYearNumber]"
HorizontalAlignment="Left" FontSize="20pt"
FontWeight="Bold" Foreground="Pink"/>
<!--Banners-->
<!-- Copy and paste the section beginning with <MonthWeekDayCalendar and ending with </MonthWeekDayCalendar> for each additional thumbnail calendar. Make changes as noted for each calendar -->
<!-- Each calendar needs a different Column number - for
4 calendars, you'll use numbers 1 through 4. -->
<MonthWeekDayCalendar Row="0" Column="1"
Height="1.1in" Width="1.25in" VerticalAlignment="Center"
HorizontalAlignment="Center" Style="BannerControl">
<!-- Change the DateOffset: -1 is last month, 0 is this
month, 1 is next month, 2 is the month after that, etc -->
<MonthFormat DateOffset="-1">
<DockPanel>
<CalendarText Orientation="Top" Text="#[@TemplateDate_BannerMonthNameYear]"
Height="0.19in" FontSize="8pt" Style="BannerTitle"/>
<WeekHeader Orientation="Top" Height="0.15in"
FontSize="10pt" Format="d" Style="BannerWeekHeader"/>
<StandardGrid Orientation="Fill" NumColumns="1"
NumRows="6" Style="BannerBody" />
</DockPanel>
</MonthFormat>
<WeekFormat>
<DockPanel>
<CalendarText Orientation="Left" Width="0.15in"
Text="#[@TemplateDate_WeekNumber]" FontSize="5pt"
Style="BannerText" HorizontalAlignment="Left"
Margin="1,0,0,0">
<ConditionalFormat Condition="ShowWeekNumber eq
'false'" Visibility="Collapsed"/>
</CalendarText>
<StandardGrid Orientation="Fill" NumRows="1"
NumColumns="7" />
</DockPanel>
</WeekFormat>
<DayFormat>
<Banner Text="#[%d]" FontSize="7pt"
VerticalAlignment="Bottom" HorizontalAlignment="Right"
Style="BannerText">
<ConditionalFormat Condition="OutsideMonthDays eq
'true'" Visibility="Collapsed"/>
<ConditionalFormat Condition="DayOfWeek eq 'sun'"
Foreground="style!WeekendColor"
ForegroundHighlight="style!WeekendColor"/>
<ConditionalFormat Condition="DayOfWeek eq 'sat'"
Foreground="style!WeekendColor"
ForegroundHighlight="style!WeekendColor"/>
</Banner>
</DayFormat>
</MonthWeekDayCalendar>
Each element in the footer (date printer, page number and username) is on a separate line at the end of the XML. You can remove any or all of these elements from the footer by deleting the line (or lines) you want removed or edit the footer to add or change text as shown below.

<!-- Standard Footer -->
<Grid Row="4" Column="1" VerticalAlignment="Top" Margin="0,4,0,0" RowSetting="Auto"
ColumnSetting="*,*,*">
<CalendarText Row="0" Column="0" Date="#[Now]" Text="Printed on #[@TemplateDocInfo_PrintTime]"
HorizontalAlignment="Left" FontSize="7pt" />
<CalendarText Row="0" Column="1" Text="Page #[@TemplateDocInfo_Page]"
HorizontalAlignment="Center" FontSize="10pt" Foreground="Blue"/>
<CalendarText Row="0" Column="2" Text="Printed by User Acct #[@TemplateDocInfo_UserName]"
HorizontalAlignment="Right" FontSize="10pt"/>
</Grid>
Show/Hide previous and next month's dates in the Monthly Calendar
UnitRestriction in the following line, from the Standard Month 01 Letter calendar, controls whether or not you'll see the dates of previous or next month. False shows the dates, True hides the dates. If the attribute is not present, the default is True (hide the dates).
<WeekGrid Orientation="Fill" NumRows="Auto" NumColumns="7" Style="LevelOneBody" UnitRestriction="false">

Calendar Printing Assistant Modifications - add your own modifications in the Comments section
Modify the Calendar Printing Assistant Templates (EMO 10/16/2008)
Templates for Calendar Printing Assistant for Outlook 2007 (from Microsoft)