file size limit in PDF attachments

I believe that the file size limitation is infinity. there are limits to file size that are related to your operating system. For example, we have customers who try to convert 20,000 5 MB image files at 600ppi and Windows falls over just reading and writing from one folder to another.

Also, most OS will not be able to 'view" a single page PDF file that is over 10 gigs.

And while I would never make a Single Multipage PDF file as big as some of my clients (I would prefer to creat smaller multipage files and create a seachable index using metadata) - I really do no think this is the issue you are running into.

This may be as simple as you do not have enough memory on your local volume to create the required temp file.

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from the PDF Reference Guide Version 1.7 Nov 2006 (Acrobat 8)

- I keep mine on my night stand.

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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 consumer application running on a particular processor and in a particular operating environment does have such limits.

If an application attempts to perform an action that exceeds one of the limits, it displays an error.

PostScript interpreters also have implementation limits, listed in Appendix B of the PostScript Language Reference, Third Edition.

It is possible to construct a PDF file that does not violate application limits but does not print on a PostScript printer.

Keep in mind that these limits vary according to the PostScript LanguageLevel, interpreter version, and the amount of memory available to the interpreter.

This appendix describes typical limits for Acrobat. 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.
PDF itself has one architectural limit:

Because ten digits are allocated to byte offsets, the size of a file is limited to 1010 bytes (approximately 10 gigabytes).

Memory limits cannot be characterized as precisely as architectural limits because the amount of available memory and the ways in which it is allocated vary from one product to another. Memory is automatically reallocated from one use to another when necessary: when more memory is needed for a particular purpose, it can be taken from memory allocated to another purpose if that memory is currently unused or its use is nonessential (a cache, for example).

Also, data is often saved to a temporary file when memory is limited. Because of this behavior, it is not possible to state limits for such items as the number of pages in a document, number of text annotations or hypertext links on a page, number of graphics objects on a page, or number of fonts on a page or in a document.