Is there a way to tell Maple to export a figure to PDF with a proper bounding box, like all of its other graphics export formats?

To export a graphics produced by Maple's plot(), I right-click on the plot, select Export, and then one of the several choices of graphics formats.  All options, other than the PDF, work fine—they produce graphics files whose bounding boxes correspond to the extents of the image.  Exporting to PDF misbehaves—it produces the equivalent of a 8.5''x11'' paper and inserts the graphics somewhere near the upper left corner.  I am absolutely at a loss to see the utility of that.  What in the world is the use of such an export?

Is there a configuration setting that tells Maple to save to PDF with a proper bounding box?  I looked around but couldn't find one.

In the attached Maple worksheet I attempt to plot the solution of an initial value problem for a first order ODE.  DEplot fails with a cryptic message.  Strangely enough, if I give the "arrows=none" option to DEplot, it produces the correct plot!

I see this behavior in Maple 17 and 18.

Maple 11, however, works fine with or without the "arrows=none" option.

Is there an explanation for this or is it a bug?

DEplot-bug.mw

The following works as intended:

restart;
diff(x^7, x$i):
seq(%, i=0..7);

Combining the two commands into one, however, does not work:

restart;
seq(diff(x^7, x$i), i=0..7);

          Error, invalid input: diff expects 2 or more arguments, but received 1

How does one explane this?  I was unable to find the reason by looking at the help page for seq().

The expression

A := (a/u*(y*exp(-y) - x*exp(-x))/(y-x) + b/u) / (c/u + d/u);

is obviously equivalent to

I typed the latter by hand since I don't know how to do it in Maple.  Is there a trick to get Maple to do the simplification as shown?

My eyesight is not what it used to be, so I would like to maginfy Maple's help window with a zoom factor of 150%.   I know how to do that by hitting Ctrl-F4.  My question is: Is it possible to save that setting somehow so that help is displayed at 150% by default?

Aside: The option Tools->Options->Interface->Default Zoom does not seem to do what I want.  For one thing, it sets the zoom factor of the main worksheet which I don't want to change.  For another thing, it affects the zoom factor of the help window in a rather mysterious way.  For instance, if I set Default Zoom to 400%, then the main window is indeed zoomed by 400% but the help window is zoomed by only 200%.

Platform: Maple 18 on Linux