I am able to successfully merge pdf files in most cases, however I am having trouble doing so with a particular set of files that are based upon the same pdf template. This is occurring using the latest version of Spire.PDF v4.6.4. Attached you'll find a zip file containing the three source pdf files, a small console app which makes use of the PdfDocument.MergeFiles method, and it also contains a "result.pdf" file which is the result that I am seeing. I excluded the referenced Spire.PDF dlls because they made the zip too large to upload here.
If you open result.pdf you'll see that the content is cut off when compared with the individual source pdf files. Note that if I change the code to open the first source pdf and then use AppendPage(PdfDocument document) method to append the other two the first page of the result will be correct, but each subsequent page will be cut off as seen here. Note that these files represent a Form 1099-MISC from the IRS, however the content is purely test data and does not represent a real person or earnings.
I've tried using a handful of online pdf file merging sites and each of them was able to successfully merge the source pdf files without any issues, so I believe that something about my pdf template is causing Spire to fail to merge them correctly. Can you please tell me what I am doing wrong? I've only been using Spire for a few weeks, so it's largely new to me.