Long answer: If you want to send a smaller file, you need to send less data. Since Photoshop is a raster editing program, it’s data is in the form of pixels. Less data means fewer pixels. Fewer pixels means aliasing and pixelization in your file.
Short answer: no.
You can try little things like not embedding a colour profile or making sure you send a PDF that is not editable in Photoshop (that embeds the entire PSD in the PDF). Other than that just play with compression settings and resample values.
In order to produce a smaller PDF file in Illustrator (or any other app) you have to lower the images quality, assuming you are using images (as you mention pixelation). The option to compress text and line art artwork already comes activated by default, so that leaves you with the settings for color and greyscale images. You have two different settings, resolution (PPI ) and Jpeg compression level (Image Quality). If the file is meant to be viewed on the screen only up to 100% size, you can lower the resolution to 100 ppi, if it is going to be printed in an office printer, you need at least 150 ppi on the images. On the Jpeg compression level (Image Quality) I never go bellow "Medium" because the Jpeg compression artifacts get too visible (depending on the images, sometimes even Medium gets a little noisy). If with these settings the file still is to big (assuming you have turned off the "Preserve Illustrator Editing capabilities" option already) you have two choices: If it is a multipage file, split the file into several PDF files with a few pages each and send those in separate mails. Or, if it is a single page file, subscribe to a free online storage account (e.g. Sugarsync.com) and upload the file there and send a link of the file to the client so that he can download it from his computer (I always do).
Hope this helps...
I usually Export > medium res ( 150ppi ) > RGB; open the .tiff in PS and Save As > Photoshop PDF > #6 Compression. Depending on the actual size of the file, you should be looking at a couple hundred k.