First of all, understand the principle and function of paper duplicate checking system. Duplicate checking system is a tool to detect text similarity. By comparing the similarity between the text to be detected and the text in the existing literature database, the originality and plagiarism of the text to be detected can be evaluated. PDF format is a common electronic document format, which is widely used in academic and scientific research fields.

Then, documents in PDF format usually contain various format information, such as font, font size, paragraph style and so on. These format information may cause the duplicate checking system to fail to correctly parse the text content, thus affecting the accuracy of the duplicate checking results. Secondly, documents in PDF format may contain pictures, tables, charts and other non-text content, which may be misjudged as text content by the duplicate checking system, resulting in false positives or false negatives. In addition, documents in PDF format may contain special processing such as encryption or compression, which may make the duplicate checking system unable to identify and analyze the text content, thus affecting the reliability of duplicate checking results.

Finally, different PDF formats will have different effects on the duplicate checking system. Some PDF documents with simple format information may have little influence on the duplicate inspection system, while some PDF documents with complex format information or non-text content may lead to false positives or false negatives in the duplicate inspection system. In addition, for encrypted or compressed PDF documents, the accuracy of the duplicate checking system will also be affected to some extent.