1. A computer program product for determining accurate document transformation, the computer program product comprising: one or more computer readable storage media; program instructions stored on the one or more computer readable storage media, the program instructions comprising: program instructions to receive a source document for transformation to a target document during an Extract Transform Load (ETL) process, wherein the source document is in a first format and the target document is in a second format; program instructions to queue the source document according to an assigned priority for the target document, wherein the assigned priority is based on a descending order of file sizes for target documents of queued source documents; program instructions to, responsive to determining the source document is next in the queue, transform content of the source document into the target document, wherein transforming the content of the source document includes transforming the content from the first format to the second format; program instructions to, responsive to determining an increased likelihood the source document was not accurately transformed to the target document based on a file size for the target document, render the source document into a non-rasterized graphical format, wherein a rendered source document represents the source document in the non-rasterized graphical format; program instructions to render the target document into a non-rasterized graphical format, wherein a rendered target document represents the target document in the non-rasterized graphical format; program instructions to compare one or more aspects of the rendered source document to corresponding one or more aspects of the rendered target document; and program instructions to determine, based at least in part on the compared one or more aspects, the source document was accurately transformed to the target document.