Sorry for the long post--I've done a lot of research for this post, so I want to
prevent any duplication of effort.  I tried to arrange the most important
information at the top.

Summary:

In Writer, when a page is formatted in landscape mode (i.e. select "Landscape"
at "Format"|"Page," "Page" tab, "Paper Format" section, "Orientation" radio
group) and margins (on the same "Page" tab, but in the "Margins" section) are
set to 0 (any units) for a printer that cannot print without margins, OOo pops
up a dialog saying "The margin settings are out of print range.  Do you still
want to apply these settings?  If the user answers "No," he/she is returned to
the "Page" tab with the margin settings "corrected" for the currently defined
printer.  However, the left and right margins seem to be reversed (on screen
only--not in the printout).

Details:

When OOo determines the smallest allowable margins (as described above) for a
landscape Letter-sized page using the HP DeskJet 5550, it sets margins at 9pts
left, 18pts top/bottom, and 36pts right.

The PPD for the HP DeskJet 5550 (attached) specifies
  *ImageableArea Letter/Letter: "18 36 594 783"
These settings can be verified at
http://hpinkjet.sourceforge.net/printmodedescr.php#PrintableArea under the
Device Class DJGenericVIP (note that the table specifies width and height of
printable area, not top/right coordinates).  This means that the page should
have margins at 36pts left, 18pts top/bottom, and 9 pts right (see
"Assumptions/Reasoning/Terminology" below).

The PostScript output created by printing the document from OOo specifies:
  %%BoundingBox: 0 0 612 792
and
  %%PageBoundingBox: 18 36 594 783
In other words, the generated PostScript is 100% correct according to the PPD. 
This also means that the 36pt margin is on the left of the document.  However,
the on-screen display of the document shows the 36pt margin (calculated
automatically as descibed above) on the right side of the document.

To duplicate:
Using the attached PPD file (may also require foomatic-rip at
http://www.linuxprinting.org/download.cgi?filename=foomatic-rip&show=0 ), follow
the instructions given in the Summary to create a Letter-sized page in landscape
orientation with the "smallest allowable margins" calculated by OOo.  Apply a
border around the page ("Format"|"Page," "Borders" tab, click on the box icon in
the "Line arrangement" section and select "OK").  Print the document to a file
and verify the BoundingBox agrees with the values in the PPD.  View the
PostScript file onscreen (i.e. with gv and ensure that the page size is set to
"Letter" (not "BBox" or "BoundingBox") to allow you to see the unprintable
border around the document.  Notice the wide margin is on the left--opposite
that shown by OOo.

Workaround:
Ignore the "white paper" beyond the margins displayed onscreen.  Because the Pos
tScript output is correct, as long as the user aligns content relative to the
"ImageableArea" (i.e. area inside the margins), the content will appear in the
correct locations when finally printed.

Recommendations:

I thought about creating a patch myself, but there are many different approaches
that can be taken for solving this problem.  Therefore, I am hoping this bug
report will start a discussion to determine the most appropriate course of action.

The easiest fix would be to fix the logic used by the display to correctly
determine the margins based on the printer info.  (Note, however, that the logic
used by psprint *is* correct--I don't know about Xprint (if it even matters
anymore) or the Windows GDI API.)  This would be the easiest solution as it
seems the logic simply reverses the values for left and right.  (Yes, I also
tested this with differing top/bottom margins and have verified that they are
handled properly--only the left/right margins are swapped and only on-screen.) 
Of course, integrating the logic into a single component which is used by
psprint and the display would be a better solution (especially if handling of
page orientation is enhanced as described below), but may not be feasible (I
don't know the code well enough to say :).

Another possibility is to enhance the handling of page orientation by adding
support for both "landscape" and "seascape" orientations.  This would make using
OpenOffice with certain printers much easier (see
"Assumptions/Reasoning/Terminology" below).

The best way to implement this change is to make it "automatic."  The PPD
specification defines a keyword "LandscapeOrientation" to specify which
transformation should be used for creating output.  The current PPD parser does
not seem to recognize this keyword.  If integrated into the parser, it's value
should default to "Plus90" (i.e. landscape) and could be used by
"GetLandscapeAngle" to determine which transformation is being used (and,
therefore, on which sides of the page each margin belongs).  This PPD
specification makes the LandscapeOrientation keyword optional, but this would
cover most situations where a difference is needed.

Another (easier to implement) approach is to make a user-configurable setting
for printing to seascape instead of landscape.  The setting cannot be in the
"Printer Properties" dialog box (since that is created automatically from the
PPD)--and would probably cause more problems that it solves if it were that easy
to find. :)  Therefore, I would recommend "hiding" the option in the "Options -
OpenOffice.org - Print" dialog box ("Tools"|"Options", "OpenOffice.org" branch,
"Print" node).  As a matter of fact, even if we implement "automatic" handling
as described above, this option would be useful to those whose PPD's do not
specify handling and who are afraid of editing PPD's.

Assumptions/Reasoning/Terminology

I am assuming that the generated PostScript is correct and the on-screen display
is incorrect.

Reasoning:
The PPD Specification (
http://partners.adobe.com/asn/developer/pdfs/tn/5003.PPD_Spec_v4.3.pdf ), page
104, section *LandscapeOrientation specifies a keyword which may be used to
specify how a print manager should rotate and tranlate the origin of the default
user space on the page to print a document in landscape orientation.  The sole
purpose for this keyword is to ensure the output is created according to page
feeding instructions on the printer or in the printer's manual (mostly important
for letter-head, 3-hole-punched pager, envelopes, etc.).  Possible values
include "Plus90," "Minus90," and "Any."

Plus90 (often called landscape) instructs the print manager to perform the
functional equivalent of
  90 rotate 0 pagewidth neg translate
(basically moves the origin from the lower-left corner to the lower-right corner
of the page and "swaps" the x and y axes).
and Minus90 (often called seascape) instructs the print manager to perform the
functional equivalent of
  90 neg rotate pageheight neg 0 translate
(moves the origin from the lower-left corner to the upper-right corner of the
page and "swaps" the x and y axes).  The diagrams below show the relationship
between Portrait, Landscape, and Sescape.  Note that the page itself (and,
therefore, the printable area of the page) is not moving--only the coordinates
we use to locate points on the page change.

Coordinate Systems - Letter size paper

Portrait
(0,792)      (612,792)
    --------------
    | :'''''''': |
    | :        : |
    | :        : |
    | :        : |
    | :        : |
    | :        : |
    | :        : |
+y  | :........: |
^   |            |
|   --------------
| (0,0)       (612,0)
'----> +x

Landscape - Plus90 - 90deg ccw
(792,612)    (792,0)
    --------------
    | :'''''''': |
    | :        : |
    | :        : |
    | :        : |
    | :        : |
    | :        : |
    | :        : |
    | :........: |  +x
    |            |   ^
    --------------   |
 (0,612)       (0,0) |
             +y <----'

Seascape - Minus90 - 90deg cw
.----> +y
|(0,0)       (0,612)
|   --------------
v   | :'''''''': |
+x  | :        : |
    | :        : |
    | :        : |
    | :        : |
    | :        : |
    | :        : |
    | :........: |
    |            |
    --------------
(792,0)      (792,612)


The "left" side of the page--regardless of orientation--has an x coordinate of 0
and the "bottom" has a y coordinate of 0 (with "right" being the side opposite
left and "top" being the side opposite bottom).  Since the DeskJet 5550 has an
ImageableArea of "18 36 594 783," a portrait page has margins of 18pts left and
right, 9pts top, and 36pts bottom.  A landscape page has margins of 18pts top
and bottom, 9pts right, and 36pts left.  A seascape page has margins of 18pts
top and bottom, 9pts left, and 36pts right.

I am using OOo version: 1.0.3.1
[SRC641_[8584]_LINUX_INTEL_cdelab25_at_4/15/03_3:56:54]