i am in the midst of doing it too, the qatar embassy in my country has been fairly helpful in pointing out what was needed. so here goes:

PCC is absolutely needed and it must be attested by the qatar embassy in your home country. the above answers are right, sometimes they check, sometimes they dont, but play it safe, better to do it, god knows we don't want to go through more hassle when in doha right?

same goes for degree attestation. they want to know you are qualified for the job and the cert you sent them is not a fake. according to recruitment specialist at http://www.jerryvarghese.com/employers_03doc.htm#Qatar

"it necessary that each new recruit shall present copies of his / her academic or technical certificates endorsed by the original institution which issued them. These certificates shall also be duly authenticated by the concerned official authorities in Qatar and the embassy of the country from where these documents are obtained. This conditions applies to all new candidates who are readily spotted for employment in positions that require academic certificates. The certified documents will be asked for upon authentication of employment contracts at the Labour Department."