Quick Answer
Why does the PDF version number matter? Different PDF versions support different features. PDF 1.4 introduced transparency; 1.5 added compressed objects; 1.7 added AES-256 encryption. Version helps diagnose compatibility and feature support.
Frequently Asked Questions
PDF version number (1.0 through 2.0), creator application, creation and modification dates, file size, page count, linearization status (web-optimized), and embedded font count.
PDF 1.4 (Acrobat 5, 2001): transparency support. PDF 1.5 (Acrobat 6, 2003): layers and compressed objects. PDF 1.6 (Acrobat 7): AES-128 encryption. PDF 1.7 (ISO 32000-1, 2008): AES-256. PDF 2.0 (ISO 32000-2, 2017): the current standard.
A linearized (web-optimized) PDF is structured so the first page loads in browsers before the rest downloads. Non-linearized PDFs must fully download before any page displays in web contexts.
Creator shows the application that originally made the document (e.g., Microsoft Word, Adobe InDesign). Producer shows the PDF-generating software. Useful for diagnosing source-specific compatibility issues.
Re-export from the originating application choosing a newer PDF compatibility level in the export settings. In Adobe Acrobat, use Save As Other and select PDF version. In Word, choose PDF/A or version in export options.