Answer supplied by Katrina Exter:

The PACS Spectrometer Quick Start Guide has a summary of all the PSF information for the PACS spectrometer, and for more detail and tables, go to the PACS Handbook (calibration chapter). The Beams section of HELL has some more information and the beam files to download.

The PACS spectrometer beams are 2-D, i.e. they are maps, one per key wavelength. The maps have a small pixel size (0.5”) so the details of the beams can be seen clearly. Bear this in mind if comparing to images created from your PACS cubes, as their spaxels/spatial pixels are usually much larger (see the PACS Products Explained document for more detail). Bear in mind that PACS pointed observations spatially under-sample the beam; mapping observations were taken to compensate for this and the spatial sampling better. (For more information on this, see the PACS Spectrometer Quick Start Guide and the PACS Handbook)  

Note that the PA of the observation is important in the shape of the beam for any single observation — the beam rotates with the PA (this is true for photometry and spectroscopy).

If you wish to know what the actual shape of a point source is on an observation, you could look at observations of point sources: some point sources (and their ObsIDs) are published in the Herschel Cross Calibration paper. 

Note that if you want to know what your point source looks like in your specific observation, the location of the source in the FoV is important. The native spaxels of the PACS IFU are 9.4”, which is more or less the size of the beam in the blue and only slightly smaller than that in the red (see the QSG for numbers). However, if a point source is offset from the centre of the FoV by even as little as 3”, this can result in slight distortions in its appearance compared to it being located dead centre.