To help explain why errors might occur with some PDF files, the following is an extract from the PDF reference manual.
IN GENERAL, PDF does not restrict the size or quantity of things described in
the file format, such as numbers, arrays, images, and so on. However, a PDF
viewer application running on a particular processor and in a particular operating
environment does have such limits. If a viewer application attempts to perform
an action that exceeds one of the limits, it will display an error.
These limits fall into two main classes:
Architectural limits. The hardware on which a viewer application executes imposes
certain constraints. For example, an integer is usually represented in 32
bits, limiting the range of allowed integers. In addition, the design of the software
imposes other constraints, such as a limit to the number of elements in an
array or string.
Memory limits. The amount of memory available to a viewer application limits
the number of memory-consuming objects that can be held simultaneously.
Errors with files from this site will generally be caused by the size of the file being too large for your viewer or system. (This will also affect printing time)
The size of the files generated is affected by the following:-
The paper size chosen - larger sizes produce larger files.
The scale chosen - smaller scale produce larger files.
The brick set chosen - brick sets with a larger selection of images produce larger files.
If you are having problems with errors try generating a file using a large scale and a brick set with a small number of images (the number of images in a brick set is shown after the brick set's name).
If the errors no longer occur then I would suggest trying a different PDF viewer such as Foxit.