It's pronounced 'aim-you-knee'!
It's also important to note that in order to avoid tiling, your custom sheet size (set in the Amyuni PDF Converter), must firstly be big enough to accommodate entire Drawing, as set by PM's sheet size.
Amyuni works in metric (and doesn't allow decimals), so you may have to temporarily change your PlotMaker Drawing Units to mm to find out the metric sizes of your imperial sheets!
For example, a 24x26 sheet, is actually 914.4 x 609.6mm, so you will have to input 915 x 610mm as your custom sheet size, in the Amyuni Properties Dialog.
Then you''ll need to set your margins to zero as Erika pointed out. This will make it 100% sure that your PDF will have no unwanted scaling or tiling, as shown in the attachment.
Cheers,
Link.