what is the threshold of getpdftext()?

we have requriment in our project , where we need read many documnets and search for partcular text in these docs,

we need know what is the limit of number docs we can pass if we loop the getpdftext() in PM asychronusly , is ther any threshold for document size for getdpftext() function has the limit and is there any performacne issue can occur while processing of mutiple pdf docs here.