Private International Law
For those interested in these matters, the interplay between US and Polish jurisdiction in a case like that is much more complicated than what has been mentioned in previous posts and is determined by a fascinating part of the law called private international law.
In a case like this, assuming that WotC does sue in the US, the answer will depend on both US private international law and then Polish Private International Law.
At first, according to the US law, the US court will decide whether it considers it has jurisdiction or not on the matter and which law it will apply (a US court could apply Polish law for example or vice-versa). This will depend on things like the presence or not of an election of forum and election of law clause in the PDF purchase contract, on where according to US law an internet copyright infringement is located (in the country where the file is uploaded or where it is illegally downloaded ?) etc.
Assuming the US court takes jurisdiction, nobody will force the defendant to appear (this is a civil matter not criminal), but if he fails to do so, he takes the risk of an ex parte judgment.
If the defendant has assets in the US, then the matter would end there since WoTC could seize these assets in the US if they obtain a favourable judgment.
If not, then WotC needs to enforce this US judgment in Poland and then this starts an entirely new process which can vary greatly depending on Polish private international law and its leniency or not about the enforcement of foreign judgment, baring the existence of a particular treaty between US and Poland (or EU). Usually, these laws will not allow the enforcement of a foreign judgment which goes against Polish public order (which may be the case if the acts of copying are legal in Poland for example) or if the US award is based on what is called "Loi de Police" i.e. laws that are in nature more of public policy than true civil matters according to the view of Polish law and a Polish court. This is the case of tax laws for example which are very rarely enforceable in foreign jurisdiction and Penal awards based on a local law, such as copyright violation are often susceptible to this line of attack as well and may not be enforceable except for the actual damages caused rather than a statutory amount. It all depends on the exact Polish laws and jurisprudence.
All of this to say that it can get quite complicated and that is why WoTC will likely seek a settlement since its goal is likely more to make an example than to recoup any real money and also why the OP, once and if he really his served with the suit, should seek local legal advice....
Hope this was not too boring for you guys ;-)