> How can I transfer a set of marks from my pc to the iPad?

In Memory-Map on the PC, right-click on the category in the Overlay Objects window.
Save-As
Next to "Save As Type", select "GPS eXchange (*.gpx)".
Select a folder where you can find the file, such as Desktop
Give the file a name, and Save

Connect your iPad/iPhone to the PC
Run iTunes if it doesn't start automatically
In iTunes, select the device in the left column,
Click the Apps tab.
Scroll to the bottom to a section that shows all the apps that support file sharing. Select Memory-Map.
Click Add
Browse and select the GPX file you saved.
The device may automatically sync. If it doesn't, click the Apply button in the bottom right.

Now on the iPad/iPhone, run Memory-Map
Tap the right-arrow toolbar button to flip the page.
Tap the Marks toolbar button
Tap Menu
Tap Load Saved Data
Select the file

As an alternative method, instead of using iTunes, you can email the gpx file to yourself and open it as an attachment in the iPad email app.